The official language of Thailand is Thai, a Tai–Kadai language closely related to Lao, Shan in Myanmar, and numerous smaller languages spoken in an arc from Hainan and Yunnan south to the Chinese border. It is the principal language of education and government and spoken throughout the country. The standard is based on the dialect of the central Thai people, and it is written in the Thai alphabet, an abugida script that evolved from the Khmer alphabet. Several other dialects exist, and coincide with the regional designations. Southern Thai is spoken in the southern provinces, and Northern Thai is spoken in the provinces that were formerly part of the independent kingdom of Lan Na.