According to Thai authors, the writing system is probably derived from the old Thai writing of the kingdom of Sukhotai. Differences in phonology of the various local Tai languages, the isolation of communities and the fact that the written language has traditionally been passed down from father to son have led to many local variants. In an attempt to reverse this development and establish a standardized system, Vietnam's various Tai people in the former Northwestern Autonomous Region were approached with a proposal that they should agree on a common standard. Together with Vietnamese researchers, a first proposal called Thống Nhất was developed, which was published in 1961 and revised in 1966. A unified and standardized version of the script was developed at a UNESCO-sponsored workshop in 2006, named "chữ Thái Việt Nam". This standardized version was then approved to be included in Unicode. From May 2008, the improved Thai script was put into official use.
Description
The script consists of 31 consonants and 14 vowels. Unlike most other abugida's or brahmic scripts, the consonants do not have an inherent vowel, and every vowel must be specified with a vowel marker. Vowels are marked with diacritic vowel markers that can appear above, below or to the left and/or right of the consonant. Some vowels carry an inherent final consonant, such as -aj/, /-am/, /-an/ and /-əw/. The script uses Latin scriptpunctuation, and also includes five special characters, one to indicate a person, one for the number "one", one to repeat the previous word, one to mark the beginning of a text and one to mark the end of a text. Traditionally, the script did not use any spacing between words as they were written in a continious flow, but spacing has become common since the 1980s.
Consonants
Initial consonant letters have both high and low forms, which are used to indicate tones. The high consonants are used for the syllable final letters -w, -y, -m, -n and -ng. The low consonant letter -k is used for final /k/- and /ʔ/-sounds, while low consonant letters -b and -d are used for final /p/ and /t/.
Vowels
The consonant character's position is marked with a circle: ◌.
Character
Name
Sound
◌ꪰ
mai kang
/a/
◌ꪱ
aa
/aː/
◌ꪲ
i
/i/
◌ꪳ
ue
/ɨ/
◌ꪴ
u
/u/
ꪵ◌
ee
/ɛ/
ꪶ◌
o
/o/
◌ꪷ
mai khit
/ɔ/
Character
Name
Sound
◌ꪸ
ia
/iᵊ/
ꪹ◌
uea
/ɨᵊ/
◌ꪺ
ua
/uᵊ/
ꪻ◌
aue
/əw/
ꪼ◌
ay
/aj/
◌ꪽ
an
/an/
◌ꪾ
am
/am/
Some additional vowels are written with a combination of two vowel characters. The following four combinations are used for Tai Dam:
Character
Sound
ꪹ◌ꪸ
/e/
ꪹ◌ꪷ
/ə/
ꪹ◌ꪱ
/aw/
◌ꪚꪾ
/ap/
Tones
Traditionally the script used no tone marks and only partially indicated tones with the high/low consonant differentiation. The reader had to guess the tone and thus meaning of a word from context. In the 1970s two tone marks were developed, called mai nueng and mai song. Tone 1 is marked with only a low consonant. Tone 4 is marked with only a high consonant. Tone 2 is marked with the first tone mark and a low consonant form. Tone 5 is marked with the first tone mark and a high consonant form. Tone 3 is marked with the second tone mark and a low consonant form. Tone 6 is marked with the second tone mark and a high consonant form.
Character
Name
Low tone
High tone
◌
–
1
4
◌꪿
mai ek
2
5
◌꫁
mai tho
3
6
◌ꫀ
mai nueng
2
5
◌ꫂ
mai song
3
6
Unicode
Proposals to encode Tai Viet script in Unicode go back to 2006. A Unicode subcommittee reviewed a February 6, 2007 proposal submitted by James Brase of SIL International for what was then called Tay Viet script. At the ISO/IEC JTC1/SC2/WG2 meeting on April 24, 2007, a revised proposal for the script, now known as Tai Viet, was accepted "as is", with support from TCVN, the Vietnam Quality & Standards Centre. Tai Viet was added to the Unicode Standard in October, 2009 with the release of version 5.2. The Unicode block for Tai Viet is U+AA80–U+AADF:
