Thai (Siamese, Central Thai) belongs to the Tai language family, a subgroup of the Kadai or Kam-Tai family. All members of the Tai family derive from a single proto-parent designated as Proto-Tai. Linguistic research has shown the area near the border of northern Vietnam and south-eastern China as the probable place of origin for the Tai languages. Today the Tai family includes languages spoken in Assam, northern Burma, all of Thailand including the peninsula, Laos, northern Vietnam and the Chinese provinces of Yunnan, Guizhou and Guangxi.
Sukhothai, established in central Thailand in the early and mid-thirteenth century, represents the first major kingdom of the Thai. The system used here prevailed at the time of the creation of the writing system by King Ramkhamhaeng (1275-1317) in the latter part of the thirteenth century.
In 1350 the centre of power shifted from Sukhothai to Ayutthaya. The Ayyutthaya period (1350-1767) saw large numbers of Sanskrit and Pali words borrowed, although this phenomenon was not strictly limited to this period. These Indic loanwords comprise a large portion of the technical vocabularies of science, government, education, religion and literature. During the Ayutthaya period, Thai began to acquire other characteristics that have led the Thai to regard their language as highly complex and stratified, difficult to acquire even for the very educated. In part, this impression grew because of the Indic loanwords. But far more central to the creation of this image was the proliferation of titles, pronouns, royal vocabulary and royal kin terminology that reflected the growing stratification and complexity of the society.
This terminology and the emphasis upon its correct use began to be standardised during the reign of King Mongkut (1851-68). Valuing adherence to ancient patterns that produced correctness in the language, Mongkut issued decrees and proclamations that formalised place names and titles.
In Thailand, Thai serves as the official national language, It is the language taught and used in the schools, the one used by the media and the one used for all government affairs. Outside of Bangkok and the central plains, other dialects and languages of the Tai family coexist with the standard: Northern Thai (Kam Muang or Yuan) in the north, Southern Thai in the south and Lao or northeastern Thai in the north-east. Still other languages such as Lue, Phuthai and Phuan are spoken as small speech islands in various parts of the country. In addition, Thailand has many minority groups who speak languages that do not belong to the Thai family.