Tai is the most widespread and best known subgroup of the Kra-Dai family (also known as Tai-Kadai or Kam-Tai). Map 38.1 shows the distribution of the Kra-Dai languages and Map 38.2 shows, in an approximate and oversimplified way, the distribution of the Tai languages (the actual linguistic geography of Tai is very complex, with much overlapping and interpenetration of languages). Tai varieties are conventionally divided into the following groups:
Southwestern, including Ahom (extinct), Khamti, Tai Nuea (Chinese Shan, Dehong Dai), Tai Long (Shan), Khuen, Tai Lue (Xishuangbanna Dai), Kam Muang (Tai Yuan, Northern Thai), Thai (Siamese, Central Thai), Southern Thai, Lao (Lao dialects in Thailand are also called ‘Northeastern Thai’), White Tai, Tai Dam (Black Tai), Red Tai and several other languages which could not be shown in Map 38.2 for lack of space.
Central, an extraordinarily diverse group of dialects known by such names as Tay, Nung and Tho. They may in fact not form a unified subgroup.
Northern, including the languages officially known in China as Bouyei (Buyi) and Zhuang (these actually appear to constitute a dialect continuum, and the name Zhuang is also, confusingly, applied to certain Central dialects), the Yay language in Vietnam, and Saek, a Northern Tai language in Laos and Thailand that shows certain phonological peculiarities that makes it superficially distinct from other Tai languages.
The total number of native speakers of Tai languages is probably somewhere in the neighbourhood of 80 million. The largest number of speakers live in Thailand, perhaps somewhere in the neighbourhood of 45 million or more (including speakers both of Thai and of other Tai languages) and the next largest number live in China, about 25 million. Smaller numbers of Tai speakers live in the other countries shown in Map 38.2. To this we should add maybe a million or more Tai speakers living in the USA, France and other Western countries, including many refugees from the Indochinese War and many who emigrated under peaceful circumstances.
