The core Thai--the Central Thai, the Northeastern Thai (Thai-Lao), the Northern Thai, and the Southern Thai--spoke dialects of one of the languages of the Tai language family. The peoples who spoke those languages--generically also referred to as Tai--originated in southern China, but they were dispersed throughout mainland Southeast Asia from Burma to Vietnam. It was conventional in the 1980s to refer to Tai-speaking peoples in Thailand as Thai (same pronunciation) with a regional or other qualifier, e.g., Central Thai. There were, however, groups in Thailand in the late twentieth century who spoke a language of the Tai family but who were not part of the core population.