Proto-Southwest-Tai language (Ancient Thai/Old Thai) is an unattested, reconstructed common ancestor (proto-language) of all the Southwest Tai languages such as modern Thai, Lao, Shan, Northern Thai, Lue, Tai Dam, and many others. The script is based on an early form of the Thai language spoken and written by the Tais and their descendants in parts of what are now Thailand, Laos, Yunnan(China), and Shan State(Burma) during the Sukhothai period (around ).
- Unlike modern Thai and Lao, there are only two tone markers: -่ low and -้ falling.
- Pali and Sanskrit letters are omitted in this script.
- Unlike modern Thai and Lao, there are only one class of consonants.
- หมา mǎa and มา maa in Modern Thai have different tone registers but the same consonant, m sound, whereas in Proto-Tai since there is only one class of consonants and two tone markers, หมา and มา, having no tone markers, both have the same mid tone register, but different consonant sounds: หมา hmaa and มา maa.
- ท่า thâa and ถ้า thâa in Modern Thai are pronounced exactly the same, in Proto-Tai ท่า and ถ้า are pronouced dàa and thâa respectively.
referenceBrown, James M. From Ancient Thai to Modern Dialects and Other Writings on Historical Thai Linguistics. Bangkok: White Lotus, 1985. Print.