This article mainly provides the names and some characteristics of the Thai sub-ethnic groups in Thanh Hoa province. Based on the published documents and fieldwork data collected in the old mountain villages of the Thai in Thanh Hoa province and from some intervillages of Northwestern Vietnam, the author shows that the Thai in Thanh Hoa province have their autonym in accordance with the geographically residential areas where they live. They prefer their autonym to the exonym of the Black Thai and White Thai named and classified by many researchers. The reasons for this are that the Thai in Thanh Hoa province on the one hand originated from different places that there are both local and migrant
on the other hand, the voice and pronunciation of the Thai in Thanh Hoa province are different from those of the Thai in Northwestern Vietnam. As a result, the culture of the Thai ethnics in Thanh Hoa province have its own features compared with the other Thai ethnics.