Sukhothai language, a kind of Thai topolect, by the end of the 18th century, they gradually diverged into regional variants, which subsequently developed into the modern Central Thai and Southern Thai.
Central Thai language or Siamese language, the sole official language in Thailand and first language of most people in Central Thailand, including Thai Chinese in Southern Thailand.
Southern Thai language, or Southern Siamese language, or Tambralinga language, language of Southern Thailand first language of most people in Southern Thailand