Reference LGR for script: Thai (Thai) lgr-second-level-thai-script-24jan24-en

This document is mechanically formatted from the above XML file for the LGR. It provides additional summary data and explanatory text. The XML file remains the sole normative specification of the LGR.

Date 2024-01-24
LGR Version 1 (Second Level Reference LGR)
Language und-Thai (Thai Script)
Unicode Version 11.0.0



  • These instructions cover how to adopt an LGR based on this reference LGR for a given zone and how to prepare the file for deposit in the IANA Repository of IDN Practices.
  • As described the IANA procedure
    an LGR MUST contain the following elements in its header:
    • Script or Language Designator (see below for guidance)
    • Version Number (this must increase with each amendment to the LGR, even if the updates are limited to the header itself)
    • Effective Date (the date at which the policy becomes applicable in operational use)
    • Registry Contact Details (contact name, email address, and/or phone number)
  • The following information is optional:
    • Document creation date
    • Applicable Domain(s)
    • Changes made to the Reference LGR before adopting

Please add or modify the following items in the XML source code for this file before depositing the document in the IANA Repository.

Meta Data

Note: version numbers start at 1. RFC 7940 recommends using simple integers. The version comment is optional, please replace or delete the default comment. Version comments may be used by some tools as part of the page header.

<version comment="[Please replace (or delete) the optional comment]">[Please fill in version number, starting at 1]</version>

<date>[Please fill in with publication date, in YYYY-MM-DD format]</date>

<validity-start>[Please fill in effective date, in YYYY-MM-DD format]</validity-start>

Note: the scope element may be repeated, so that the same document can serve for multiple domains.

<scope type="domain">[Please provide, in ".domain" format]</scope>

Registry Contact Information:

Please fill in the Registry Contact Details.

Change History

If you made technical modifications to the LGR, please summarize them in the Change History (and also note the details in the appropriate section of the description).


Registry Contact Details

Label Generation Rules for the Thai Script


This document specifies a set of Label Generation Rules (LGR) for the Thai script for the second level domain or domains identified above. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Thai]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Thai Script” [Ref-LGR-und-Thai], for details, see Change History below.

For details and additional background on the Thai script, see “Proposal for a Thai Script Root Zone LGR” [Proposal-Thai].


The repertoire contains 68 code points for letters used in the Thai language. In addition, three sequences have been defined. The sequence U+0E4D U+0E32  ํา  was defined to replace the disallowed U+0E33 SARA AM and to facilitate implementation of the WLE rule follows-consonant-tone as a context rule. The other two sequences were defined to restrict U+0E45 LAKKHANGYAO from appearing in any context other than these sequences. Accordingly, while U+0E45 is not listed by itself this brings the total of code points avaliable for letters to 69.

The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Thai]. (The proposal cited has been adopted for the Thai script portion of the Root Zone LGR.)

For the second level, the repertoire has been augmented with the ASCII digits, U+0030 0 to U+0039 9; Thai digits, U+0E50 to U+0E59 ; U+002D - HYPHEN-MINUS; the abbreviation mark U+0E2F THAI CHARACTER PAIYANNOI; and the repetition mark U+0E46 THAI CHARACTER MAIYAMOK. Also, a special sequence using the abbreviation mark has been added for a total of 95 repertoire elements.

Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used, and one or more references documenting sufficient justification for inclusion in the repertoire, see “References” below. Comments provide additional information for some code points.


The variants defined in this LGR are limited to those required for use in zones not shared with any other script. However, because it does not share cross-script variants with other script LGRs, this LGR can be mixed easily with other LGRs in the same zone.

This LGR defines no variants for letters, see Section 6, “Variants” in [Proposal-Thai].

Digit Variants: All Thai digits are treated as semantic variants of the corresponding common (ASCII) digits. By transitivity, they are also semantic variants of any native digits in scripts that also include the common digits. Such variant relations are deemed to exist implicitly by transitivity but are not listed explicitly in each reference LGR. Instead, if needed, they are applied by using the Common LGR in label processing.

In particular, Thai digit ZERO is a cross-script homoglyph or near homoglyph of digit ZERO in many other scripts; these are already implicit semantic variants by transitivity and therefore not listed here.

There is a strong resemblance between Thai and Khmer digits, as well as with certain Lao digits.

To keep digit variant sets manageable in zones where multiple scripts are present, no attempt has been made at identifying cross-script variants among digits of different numeric value or between a digit in one script and a letter in another, such as between digit zero and Latin letter ‘o’. Other mechanisms may be required to prevent homograph labels.

Character Classes

The Thai Script is an abugida in which consonant–vowel sequences are written as a unit: each unit is based on a consonant letter, and vowel, tone mark or diacritic notation are secondary. It is written with the combining marks stacked above or below the base consonant, like diacritics in European languages. However, although the concepts are quite similar, the implementations are significantly different.

Consonants: There are 44 characters that are classified as consonants; code points from this subset have been given the tag “cons”. See Section 5.1, “Consonants” in [Proposal-Thai].

Vowels: The 18 vowel symbols pronounced after a consonant are non-sequential: they can be located before (lv) , after (fv), above (av) or below (bv) the consonant, or in a combination of these positions, code points from this subset have been given the tags “fv1”,"fv2", “fv3”, “av”, “bv”, or “lv”. There are three code point sequences defined that include vowels. (Code point sequences do not carry tag values; instead, for code point sequences the subset values are identified in comments). See Section 5.2, “Vowels” in [Proposal-Thai].

Tones: There are 5 phonemic tones: mid, low, falling, high, and rising. These 5 tones are represented by 4 tone marks plus the absence of a mark. Code points from this subset have been given the tag “tone”. See section 5.3, “Tone Marks” in [Proposal-Thai].

Diacritical Marks: There are 3 above diacritic symbols that have been included here and given the tag “ad”. They differ in their frequency and purpose of usage. See also the discussion in Section 5.,4 “Diacritics” in [Proposal-Thai].

  • U+0E47  ็  MAITAIKHU and U+0E4C  ์  THANTHAKHAT are commonly used for words in everyday communication
  • U+0E4D  ํ  NIKHAHIT is included because of its use to decompose U+0E33 THAI CHARACTER SARA AM, which is in common use. However, NIKHAHIT may also be used by itself.

A fourth above diacritic, U+0E4E  ๎  YAMAKKAN, has been excluded from the Root Zone LGR repertoire because it is rarely used in Modern Thai or even in older Pali manuscripts; it is more common to replace it with U+0E3A  ฺ  PHINTHU, a below diacritic, which has been given the tag “bd”. Moreover, excluding U+0E4E  ๎  YAMAKKAN also eliminates the chance of confusion between U+0E4E  ๎  YAMAKKAN and U+0E4C  ์  THANTHAKHAT. Both look similar, are always placed at the same position in the word cell, and they are normally displayed in a small size.

Abbreviation Mark: The abbreviation mark (or ellipsis) U+0E2F PAIYANNOI should not be at the beginning position and must end the label. An exception to this rule has been provided for by a special sequence.

Repetition Mark: The repetition mark U+0E46 MAIYAMOK repeats anything before it. Therefore, it should not be at the beginning position. The repetition mark must not be followed by any combining mark, or follow a leading vowel to prevent unstable rendering. A repetition mark may be repeated. A context rule has been defined to limit the repetition mark to acceptable context, however, some of the restrictions are taken care of by other rules, for example, the rule that leading vowel must be followed by a consonant.

Thai Digits: U+0E50 to U+0E59 are a set of Thai-specific digits. They are used in alternation with the European (common) digits.

Common Digits: U+0030 0 to U+0039 9 are the set of digits from the ASCII range.

Whole Label Evaluation (WLE) and Context Rules

Common Rules

The LGR includes the rules and actions to implement the following restrictions, some of which are mandated by the IDNA protocol. They are marked with ⍟ and included here by default.

  • Hyphen Restrictions — restrictions on the allowable placement of hyphens (no leading/ending hyphen and no hyphen in positions 3 and 4). These restrictions are described in Section of RFC 5891 [150]. They are implemented here as context rule on U+002D (-) HYPHEN-MINUS.
  • Leading Combining Marks — restrictions on the allowable placement of combining marks (no leading combining mark). This rule is described in Section of RFC 5891 [150].
  • Digit-mixing — no mixing between different digit sets (European and Thai digits) is allowed; implemented here as a WLE rule with associated action.

Default Actions

This LGR includes the complete set default actions for LGRs as well as the action needed to invalidate labels with misplaced combining marks. They are marked with ⍟. For a description see [RFC 7940] and [150]. An additional action is triggered by mixed digit labels.

Thai-specific Rules

The rules provided in this LGR as described in Section 7 of [Proposal-Thai] reasonably restrict labels so that they conform to Thai syllable structure. These constraints are exclusively presented as context rules.

The rules are:

  • A leading-vowel must precede a consonant — See Section 7.2 in [Proposal-Thai]
  • A below-vowel must follow a consonant — See Section 7.3 in [Proposal-Thai]
  • An above-vowel must follow a consonant — See Section 7.3 in [Proposal-Thai]
  • A below diacritic must follow a consonant — See Section 7.3 in [Proposal-Thai]
  • An above-diacritic MAITAIKHU must follow a consonant — See Section 7.3 in [Proposal-Thai]
  • A vowel MAIHAN AKAT must be in between a consonant and either tone or consonant — See Section 7.4 in [Proposal-Thai]
  • A vowel SARA A can follow a consonant, a tone or a vowel SARA AA — See Section 7.5 in [Proposal-Thai]
  • A vowel SARA AA, or an above diacritic NIKHAHIT followed by a vowel SARA AA can follow a consonant or a tone — See Sections 7.6 and 7.9 in [Proposal-Thai]
  • A tone mark, THANTHAKHAT, NIKHAHIT can only follow a consonant, above-vowel or below-vowel — See section 7.7 and 7.8 in [Proposal-Thai]
  • An abbreviation mark, PAIYANNOI cannot be at the beginning of the label and must end it — rule SL1 for second level
  • A repetition mark, MAIYAMOK can precede a repetition mark, an independent vowel, or end of label; it cannot start a label — rule SL2 for second level

Methodology and Contributors

The LGR in this document has been adapted from the corresponding Reference LGR for the Second Level. The Second Level Reference LGR for the Thai Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Thai script and information contained or referenced therein; see [RZ-LGR-Thai]. Suitable extensions for the second level have been applied according to the [Guidelines] and with community input. As part of that process, features have been removed or modified as appropriate for the target language. The original proposal for a Root Zone LGR for the Thai script, that this LGR is based on, was developed by the Thai Generation Panel. For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Thai], as well as [RZ-LGR-Overview].

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Thai Script [Ref-LGR-und-Thai] without normative changes.


The following general references are cited in this document:

ICANN, “Guidelines for Developing Reference LGRs for the Second Level”, (Los Angeles, California: ICANN, 27 May 2020),
Internet Corporation for Assigned Names and Numbers, (ICANN),“Reference Label Generation Rules (LGR) for the Second Level: Overview and Summary” (PDF), (Los Angeles, California: ICANN, 24 January 2024),
Proposal for a Thai Script Root Zone LGR, 25 May 2017,
ICANN, Second Level Reference Label Generation Rules for the Thai Script (und-Thai), 24 January 2024 (XML)
non-normative HTML presentation:
[RFC 7940]
Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
[RFC 8228]
A. Freytag, “Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels”, RFC 8228, August 2017,
Integration Panel, “Root Zone Label Generation Rules (RZ LGR-5): Overview and Summary”, 26 May 2022 (PDF),
ICANN, Root Zone Label Generation Rules for the Thai Script (und-Thai), 26 May 2022 (XML)
[Unicode 11.0.0]
The Unicode Consortium. The Unicode Standard, Version 11.0.0, (Mountain View, CA: The Unicode Consortium, 2018. ISBN 978-1-936213-19-1)

For references consulted particularly in designing the repertoire for the Thai Script for the second level please see details in the Table of References below.

Reference [0] refers to the Unicode Standard version in which corresponding code points were initially encoded. References [100] and [101] correspond to sources given in [Proposal-Thai] for justifying the inclusion of for the corresponding code points. Entries in the table may have multiple source reference values. In the listing of whole label evaluation and context rules, reference [150] indicates the source for common rules.


Repertoire Summary

Number of elements in repertoire 95
Number of code points
for each script
Thai 80
Common 11
Number of code points 91
Number of sequences 4
Longest code point sequence 3
Code points defined via sequence 1

Repertoire by Code Point

The following table lists the repertoire by code point (or code point sequence). The data in the Script and Name column are extracted from the Unicode character database. Where a comment in the original LGR is equal to the character name, it has been suppressed.

Some code points that may be part of a valid label under this LGR only occur as part of one or more sequences. Such code points are not listed individually in the table.

For any code point or sequence for which a variant is defined, additional information is provided in the Variants column. See also the legend provided below the table.

Glyph Script Name Ref Tags Required Context Variants Comment
U+002D - Common HYPHEN-MINUS [0]   not: hyphen-minus-disallowed  
U+0030 0 Common DIGIT ZERO [0] Common-digit   set 1
U+0031 1 Common DIGIT ONE [0] Common-digit   set 2
U+0032 2 Common DIGIT TWO [0] Common-digit   set 3
U+0033 3 Common DIGIT THREE [0] Common-digit   set 4
U+0034 4 Common DIGIT FOUR [0] Common-digit   set 5
U+0035 5 Common DIGIT FIVE [0] Common-digit   set 6
U+0036 6 Common DIGIT SIX [0] Common-digit   set 7
U+0037 7 Common DIGIT SEVEN [0] Common-digit   set 8
U+0038 8 Common DIGIT EIGHT [0] Common-digit   set 9
U+0039 9 Common DIGIT NINE [0] Common-digit   set 10
U+0E01 Thai THAI CHARACTER KO KAI [0], [100], [101] cons     Thai
U+0E02 Thai THAI CHARACTER KHO KHAI [0], [100], [101] cons     Thai
U+0E03 Thai THAI CHARACTER KHO KHUAT [0], [100], [101] cons     Thai
U+0E04 Thai THAI CHARACTER KHO KHWAI [0], [100], [101] cons     Thai
U+0E05 Thai THAI CHARACTER KHO KHON [0], [100], [101] cons     Thai
U+0E06 Thai THAI CHARACTER KHO RAKHANG [0], [100], [101] cons     Thai
U+0E07 Thai THAI CHARACTER NGO NGU [0], [100], [101] cons     Thai
U+0E08 Thai THAI CHARACTER CHO CHAN [0], [100], [101] cons     Thai
U+0E09 Thai THAI CHARACTER CHO CHING [0], [100], [101] cons     Thai
U+0E0A Thai THAI CHARACTER CHO CHANG [0], [100], [101] cons     Thai
U+0E0B Thai THAI CHARACTER SO SO [0], [100], [101] cons     Thai
U+0E0C Thai THAI CHARACTER CHO CHOE [0], [100], [101] cons     Thai
U+0E0D Thai THAI CHARACTER YO YING [0], [100], [101] cons     Thai
U+0E0E Thai THAI CHARACTER DO CHADA [0], [100], [101] cons     Thai
U+0E0F Thai THAI CHARACTER TO PATAK [0], [100], [101] cons     Thai
U+0E10 Thai THAI CHARACTER THO THAN [0], [100], [101] cons     Thai
U+0E11 Thai THAI CHARACTER THO NANGMONTHO [0], [100], [101] cons     Thai
U+0E12 Thai THAI CHARACTER THO PHUTHAO [0], [100], [101] cons     Thai
U+0E13 Thai THAI CHARACTER NO NEN [0], [100], [101] cons     Thai
U+0E14 Thai THAI CHARACTER DO DEK [0], [100], [101] cons     Thai
U+0E15 Thai THAI CHARACTER TO TAO [0], [100], [101] cons     Thai
U+0E16 Thai THAI CHARACTER THO THUNG [0], [100], [101] cons     Thai
U+0E17 Thai THAI CHARACTER THO THAHAN [0], [100], [101] cons     Thai
U+0E18 Thai THAI CHARACTER THO THONG [0], [100], [101] cons     Thai
U+0E19 Thai THAI CHARACTER NO NU [0], [100], [101] cons     Thai
U+0E1A Thai THAI CHARACTER BO BAIMAI [0], [100], [101] cons     Thai
U+0E1B Thai THAI CHARACTER PO PLA [0], [100], [101] cons     Thai
U+0E1C Thai THAI CHARACTER PHO PHUNG [0], [100], [101] cons     Thai
U+0E1D Thai THAI CHARACTER FO FA [0], [100], [101] cons     Thai
U+0E1E Thai THAI CHARACTER PHO PHAN [0], [100], [101] cons     Thai
U+0E1F Thai THAI CHARACTER FO FAN [0], [100], [101] cons     Thai
U+0E20 Thai THAI CHARACTER PHO SAMPHAO [0], [100], [101] cons     Thai
U+0E21 Thai THAI CHARACTER MO MA [0], [100], [101] cons     Thai
U+0E22 Thai THAI CHARACTER YO YAK [0], [100], [101] cons     Thai
U+0E23 Thai THAI CHARACTER RO RUA [0], [100], [101] cons     Thai
U+0E24 Thai THAI CHARACTER RU [0], [100], [101] fv3     Thai
U+0E24 U+0E45 ฤๅ {Thai} THAI CHARACTER RU + THAI CHARACTER LAKKHANGYAO [0], [100], [101] [fv3] + U+0E45     fv2, Thai
U+0E25 Thai THAI CHARACTER LO LING [0], [100], [101] cons     Thai
U+0E26 Thai THAI CHARACTER LU [0], [100], [101] fv3     Thai
U+0E26 U+0E45 ฦๅ {Thai} THAI CHARACTER LU + THAI CHARACTER LAKKHANGYAO [0], [100], [101] [fv3] + U+0E45     fv2, Thai
U+0E27 Thai THAI CHARACTER WO WAEN [0], [100], [101] cons     Thai
U+0E28 Thai THAI CHARACTER SO SALA [0], [100], [101] cons     Thai
U+0E29 Thai THAI CHARACTER SO RUSI [0], [100], [101] cons     Thai
U+0E2A Thai THAI CHARACTER SO SUA [0], [100], [101] cons     Thai
U+0E2B Thai THAI CHARACTER HO HIP [0], [100], [101] cons     Thai
U+0E2C Thai THAI CHARACTER LO CHULA [0], [100], [101] cons     Thai
U+0E2D Thai THAI CHARACTER O ANG [0], [100], [101] cons     Thai
U+0E2E Thai THAI CHARACTER HO NOKHUK [0], [100], [101] cons     Thai
U+0E2F Thai THAI CHARACTER PAIYANNOI [0], [100], [101] abbr follows-any-precedes-end   Thai
U+0E2F U+0E25 U+0E2F ฯลฯ {Thai} THAI CHARACTER PAIYANNOI + THAI CHARACTER LO LING + THAI CHARACTER PAIYANNOI [0], [100], [101] [abbr] + [cons] + [abbr] follows-any-precedes-end   Thai
U+0E30 Thai THAI CHARACTER SARA A [0], [100], [101] fv1 follow-consonant-tone-sara-aa   Thai
U+0E31  ั Thai THAI CHARACTER MAI HAN-AKAT [0], [100], [101] av between-consonant-and-ct   Thai
U+0E32 Thai THAI CHARACTER SARA AA [0], [100], [101] fv1, sara-aa follows-consonant-tone   Thai
U+0E34  ิ Thai THAI CHARACTER SARA I [0], [100], [101] av follows-consonant   Thai
U+0E35  ี Thai THAI CHARACTER SARA II [0], [100], [101] av follows-consonant   Thai
U+0E36  ึ Thai THAI CHARACTER SARA UE [0], [100], [101] av follows-consonant   Thai
U+0E37  ื Thai THAI CHARACTER SARA UEE [0], [100], [101] av follows-consonant   Thai
U+0E38  ุ Thai THAI CHARACTER SARA U [0], [100], [101] bv follows-consonant   Thai
U+0E39  ู Thai THAI CHARACTER SARA UU [0], [100], [101] bv follows-consonant   Thai
U+0E3A  ฺ Thai THAI CHARACTER PHINTHU [0], [100], [101] bd follows-consonant   = phinthu; Thai
U+0E40 Thai THAI CHARACTER SARA E [0], [100], [101] lv precedes-consonant   Thai
U+0E41 Thai THAI CHARACTER SARA AE [0], [100], [101] lv precedes-consonant   Thai
U+0E42 Thai THAI CHARACTER SARA O [0], [100], [101] lv precedes-consonant   Thai
U+0E43 Thai THAI CHARACTER SARA AI MAIMUAN [0], [100], [101] lv precedes-consonant   Thai
U+0E44 Thai THAI CHARACTER SARA AI MAIMALAI [0], [100], [101] lv precedes-consonant   Thai
U+0E46 Thai THAI CHARACTER MAIYAMOK [0], [100], [101] rep follows-any-precedes-rep-cons-lv-end   Thai
U+0E47  ็ Thai THAI CHARACTER MAITAIKHU [0], [100], [101] ad follows-consonant   = maitaikhu; Thai
U+0E48  ่ Thai THAI CHARACTER MAI EK [0], [100], [101] tone follows-consonant-av-bv   Thai
U+0E49  ้ Thai THAI CHARACTER MAI THO [0], [100], [101] tone follows-consonant-av-bv   Thai
U+0E4A  ๊ Thai THAI CHARACTER MAI TRI [0], [100], [101] tone follows-consonant-av-bv   Thai
U+0E4B  ๋ Thai THAI CHARACTER MAI CHATTAWA [0], [100], [101] tone follows-consonant-av-bv   Thai
U+0E4C  ์ Thai THAI CHARACTER THANTHAKHAT [0], [100], [101] ad follows-consonant-av-bv   = thanthakhat; Thai
U+0E4D  ํ Thai THAI CHARACTER NIKHAHIT [0], [100], [101] ad follows-consonant-av-bv   = nikhahit; Thai
U+0E4D U+0E32  ํา {Thai} THAI CHARACTER NIKHAHIT + THAI CHARACTER SARA AA [0], [100], [101] [ad] + [fv1, sara-aa] follows-consonant-tone   = sara am sequence; Thai
U+0E50 Thai THAI DIGIT ZERO [0] Thai-digit   set 1  
U+0E51 Thai THAI DIGIT ONE [0] Thai-digit   set 2  
U+0E52 Thai THAI DIGIT TWO [0] Thai-digit   set 3  
U+0E53 Thai THAI DIGIT THREE [0] Thai-digit   set 4  
U+0E54 Thai THAI DIGIT FOUR [0] Thai-digit   set 5  
U+0E55 Thai THAI DIGIT FIVE [0] Thai-digit   set 6  
U+0E56 Thai THAI DIGIT SIX [0] Thai-digit   set 7  
U+0E57 Thai THAI DIGIT SEVEN [0] Thai-digit   set 8  
U+0E58 Thai THAI DIGIT EIGHT [0] Thai-digit   set 9  
U+0E59 Thai THAI DIGIT NINE [0] Thai-digit   set 10  


Throughout this LGR, a code point sequence may be annotated with a string in ALL CAPS that is constructed on the same principle as a name for a Unicode Named Sequence. No claim is made that a sequence thus annotated is in fact a named sequence, nor that the annotation in such case actually corresponds to the formal name of a named sequence.

Code Point
A code point or code point sequence.
The shape displayed depends on the fonts available to your browser.
Shows the script property value from the Unicode Character Database. Combining marks may have the value Inherited and code points used with more than one script may have the value Common. Sequences are annotated with a set of all distinct script values.
Shows the character or sequence name from the Unicode Character Database. Named sequences are listed with their normative names, for ad-hoc sequences the individual names are shown separated by “+”.
Links to the references associated with the code point or sequence, if any.
LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view. For sequences, the tags for all member code points are shown in [] for information; sequences as such do not have tags.
Required Context
Link to a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:” identifies a context that must not occur.
Link to the variant set the code point or sequence is a member of, except where a coded point or sequence maps only to itself, in which case the type of that mapping is listed.
The comment as given in the XML file. However, if the comment for this row consists only of the code point or sequence name, it is suppressed in this view. By convention, comments starting with “=” denote an alias. If present, the symbol ⍟ marks a default item shared among a set of LGRs.


Variant Set Summary

Number of variant sets 10
Largest variant set 2
Variants by Type
blocked 20

Variant Sets

The following tables list all variant sets defined in this LGR, except for singleton sets. Each table lists all variant mapping pairs of the set; one per row. Mappings are assumed to be symmetric: each row documents both forward (→) and reverse (←) mapping directions. In each table, the mappings are sorted by Source value in ascending code point order; shading is used to group mappings from the same source code point or sequence.

Where the type of both forward and reverse mappings are the same, a single value is given in the Type column; otherwise the types for forward and reverse mappings, as well as comments and references, are listed above one another. For summary counts, both forward and reverse mappings are always counted separately.

In any LGR with variant specifications that are well behaved, all members within each variant set are defined as variants of each other; the mappings in each set are symmetric and transitive; and all variant sets are disjoint.

Common Legend

By convention, the smaller of the two code points in a variant mapping pair.
By convention, the larger of the two code points in a variant mapping pair.
The shape displayed for source or target depends on the fonts available to your browser.
- forward
Indicates that Type, Ref and Comment apply to the mapping from source to target.
- reverse
Indicates that Type, Ref and Comment apply to the reverse mapping from target to source.
- both
Indicates that Type, Ref and Comment apply to both forward and reverse mapping.
The type of the variant mapping, including predefined variant types such as “allocatable” and “blocked”; or any that are defined specifically for this LGR.
One or more reference IDs (optional). A “/” separates references for reverse / forward mappings, if different.
A descriptive comment (optional). A “/” separates comments for reverse / forward mappings, if different.

Variant Set 1 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0030 0 0E50 blocked   ASCII digit variant / Thai digit variant

Variant Set 2 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0031 1 0E51 blocked   ASCII digit variant / Thai digit variant

Variant Set 3 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0032 2 0E52 blocked   ASCII digit variant / Thai digit variant

Variant Set 4 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0033 3 0E53 blocked   ASCII digit variant / Thai digit variant

Variant Set 5 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0034 4 0E54 blocked   ASCII digit variant / Thai digit variant

Variant Set 6 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0035 5 0E55 blocked   ASCII digit variant / Thai digit variant

Variant Set 7 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0036 6 0E56 blocked   ASCII digit variant / Thai digit variant

Variant Set 8 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0037 7 0E57 blocked   ASCII digit variant / Thai digit variant

Variant Set 9 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0038 8 0E58 blocked   ASCII digit variant / Thai digit variant

Variant Set 10 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0039 9 0E59 blocked   ASCII digit variant / Thai digit variant

Classes, Rules and Actions

Character Classes

Number of named classes 12
Implicit (except script) 5
Implict defined by script tag 2

The following table lists all named and implicit classes with their definition and a list of their members intersected with the current repertoire (for larger classes, this list is elided).

Name Definition Count Members or Ranges Ref Comment
above-vowel Tag=av 5 {0E31 0E34-0E37}   Any Thai above vowel
below-vowel Tag=bv 2 {0E38-0E39}   Any Thai below vowel
consonant Tag=cons 44 {0E01-0E23 0E25 0E27-0E2E}   Any Thai consonant
leading-vowel Tag=lv 5 {0E40-0E44}   Any Thai leading vowel
repetition Tag=rep 1 {0E46}   The Thai repetition mark, MAIYAMOK
sara-aa Tag=sara-aa 1 {0E32}   Thai SARA AA
tone Tag=tone 4 {0E48-0E4B}   Any Thai tone mark
c-av-bv combined =
[[:consonant:] ∪ [:above-vowel:] ∪ [:below-vowel:]]
51 {0E01-0E23 0E25 0E27-0E2E 0E31 0E34-0E39}   Any Thai consonant, vowel-above or vowel-below
ct combined =
[[:consonant:] ∪ [:tone:]]
48 {0E01-0E23 0E25 0E27-0E2E 0E48-0E4B}   Any Thai consonant or tone mark
ctaa combined =
[[:consonant:] ∪ [:tone:] ∪ [:sara-aa:]]
49 {0E01-0E23 0E25 0E27-0E2E 0E32 0E48-0E4B}   Any Thai consonant, tone or sara-aa
common-digits Tag=Common-digit 10 {0030-0039}   Digits from the ASCII range; ⍟
thai-digits Tag=Thai-digit 10 {0E50-0E59}   Thai digits
implicit Tag=abbr 1 {0E2F}   The character tagged as abbr
implicit Tag=ad 3 {0E47 0E4C-0E4D}   Any character tagged as ad
implicit Tag=bd 1 {0E3A}   The character tagged as bd
implicit Tag=fv1 2 {0E30 0E32}   Any character tagged as fv1
implicit Tag=fv3 2 {0E24 0E26}   Any character tagged as fv3
implicit Tag=sc:Thai 80 {0E01-0E32 0E34-0E3A 0E40-0E44 0E46-0E4D 0E50-0E59}   Any character tagged as Thai
implicit Tag=sc:Zyyy 11 {002D 0030-0039}   Any character tagged as Common


Members or Ranges
Lists the members of the class as code points (xxx) or as ranges of code points (xxx-yyy). Any class too numerous to list in full is elided with "...".
A named or implicit class defined by all code points that share the given tag value (ttt).
An anonymous class implicitly defined based on tag value and for which there is no named equivalent.
A named class defined by set operations on other classes using the following syntax:
[: :] - named or implicit character set
Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
∪, ∩, ∖, ∆ - set operators
Sets may be combined by set operators ( = union, = intersection, = difference, = symmetric difference).

Whole label evaluation and context rules

Number of rules 11
Used to trigger actions 2
Used as context rule (C) 9
Anchored context rules 9

The following table lists all named rules defined in the LGR and indicates whether they are used as trigger in an action or as context (when or not-when) for a code point or variant.

Name Regular Expression Used as
Anchor Used as
Ref Comment
leading-combining-mark (start)[[\p{gc=Mn}] ∪ [∅=\p{gc=Mc}]]     [150] RFC 5891 restrictions on placement of combining marks ⍟
hyphen-minus-disallowed (((start))← ⚓︎)|(⚓︎ →((end)))|(((start)..\u002D)← ⚓︎)   C [150] RFC 5891 restrictions on placement of U+002D -
precedes-consonant ⚓︎ →([:consonant:])   C   WLE 7.2: check if current cp is preceding a consonant
follows-consonant ([:consonant:])← ⚓︎   C   WLE 7.3: check if current cp is following a consonant
between-consonant-and-ct ([:consonant:])← ⚓︎ →([:ct:])   C   WLE 7.4: check if current cp is in between a consonant and either tone or consonant
follow-consonant-tone-sara-aa ([:ctaa:])← ⚓︎   C   WLE 7.5: U+0E30 THAI CHARACTER SARA A can follow a consonant, a tone or U+0E32 THAI CHARACTER SARA AA
follows-consonant-tone ([:ct:])← ⚓︎   C   WLE 7.6, 7.9: check if current cp is following a consonant or a tone
follows-consonant-av-bv ([:c-av-bv:])← ⚓︎   C   WLE 7.7, 7.8: A tone-mark, THANTHAKHAT, NIKAHIT can only follow a consonant, above-vowel or below-vowel
follows-any-precedes-end (.)← ⚓︎ →((end))   C [102] WLE SL1: An abbreviation mark, PAIYANNOI cannot be at the beginning of the label and must end it
follows-any-precedes-rep-cons-lv-end (.)← ⚓︎ →([:consonant:]|[:repetition:]|[:leading-vowel:]|(end))   C [102] WLE SL2: A repetition mark, MAIYAMOK cannot be at the beginning of the label and must be followed by itself, a consonat or a leading vowel
digit-mixing ([:common-digits:].*[:thai-digits:])|([:thai-digits:].*[:common-digits:])       restrictions on mixing digits


Used as Trigger
This rule triggers one of the actions listed below.
Used as Context
This rule defines a required or prohibited context for a code point C or variant V.
This rule has a placeholder for the code point for which it is evaluated.
Regular Expression
A regular expression equivalent to the rule, shown in a modified notation as noted:
⚓︎ - context anchor
Placeholder for the actual code point when a context is evaluated. The code point must occur at the position corresponding to the anchor. Rules containing an anchor cannot be used as triggers.
(...)← - look-behind
If present encloses required context preceding the anchor.
→(..) - look-ahead
If present encloses required context following the anchor.
( ) - group
An anonymous nested rule is used to group match operators.
(... | ...) - choice
When there is more than one alternative in a rule, the choices are separated by the alternation operator (...|...).
start or end
(start) matches the start of the label; (end) matches the end of the label.
. - any code point
. matches any code point.
*, +, ?, {n,m} - count operators
* indicates 0 or more, + indicates one or more, and ? indicates up to one instance. {n,m} indicates at least n and at most m instances.
[: :] - named or implicit character set
Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
[\p{ }] - property
Set of all characters matching a given value for a Unicode property [\p{prop=val}]. Note: uppercase “\P” defines the complement of a property set.
∪, ∩, ∖, ∆ - set operators
Sets may be combined by set operators ( = union, = intersection, = difference, = symmetric difference).
∅= - empty set
Indicates that the following set is empty because of the result of set operations, or because none of its elements is part of the repertoire defined here. A rule with a non-optional empty set never matches.
⍟ - default rule
Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.


The following table lists the actions that are used to assign dispositions to labels and variant labels based on the specified conditions. The order of actions defines their precedence: the first action triggered by a label is the one defining its disposition.

# Condition Rule / Variant Set   Disposition Ref Comment
1 if label matches leading-combining-mark invalid [150] labels with leading combining marks are invalid ⍟
2 if label matches digit-mixing invalid   a label violating the restriction on digit mixing is invalid
3 if at least one variant is in {out-of-repertoire-var} invalid   any variant label with a code point out of repertoire is invalid ⍟
4 if at least one variant is in {blocked} blocked   any variant label containing blocked variants is blocked ⍟
5 if each variant is in {allocatable} allocatable   variant labels with all variants allocatable are allocatable ⍟
6 if any label (catch-all)   valid   catch all (default action) ⍟


{...} - variant type set
In the “Rule/Variant Set” column, the notation {...} means a set of variant types.
⍟ - default action
Actions marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, out-of-repertoire-var. This is not necessarily an error.

Table of References

The following lists the references cited for specific code points, variants, classes, rules or actions in this LGR. For General references refer to the References section in the Description.

[0] The Unicode Standard, Version 1.1
Any code point originally encoded in Unicode 1.1
[100] Thai Industrial Standard (TIS) 1566-2541(1988)
[101] Computers and the Thai Language
[102] Thai Generation Panel experts, private communication during review for second level
[150] RFC 5891, Internationalized Domain Names in Applications (IDNA): Protocol