Thai (ภาษาไทย Phasa Thai[pʰāːsǎː tʰāj] ( listen)), more precisely Central Thai or Siamese, is the national and official language of Thailand and the native language of the Thai people, Thailand's dominant ethnic group. Thai is a member of the Tai group of the Tai–Kadai language family. Some words in Thai are borrowed from Pali, Sanskrit and Old Khmer. It is a tonal and analytic language. Thai also has a complex orthography and relational markers.^{[citation needed]} Thai is mutually intelligible with Lao.

Thai is the official language of Thailand, spoken by over 20 million people (2000),Standard Thai is based on the register of the educated classes of Bangkok.Khorat Thai is spoken by about 400,000 (1984) in Nakhon Ratchasima; it occupies a linguistic position somewhere between Siamese Thai and Isan on a dialect continuum, and may be considered a variant of either. A majority of the people in the Isan region of Thailand speak a dialect of the Lao language, which has influenced the Siamese Thai dialect.^{[citation needed]}

Thai Chinese are Thai citizens of Chinese, - primarily of Han Chinese - origin. Thailand is home to the second largest Overseas Chinese community after the Chinese community Indonesia. It is the oldest, most prominent, and well integrated overseas Chinese community in the world with a population of approximately eight million accounting for 12% of the Thai population as of 2011. Most Thai Chinese have been in Thailand for five generations or more; the Thai-Chinese have been deeply ingrained into all elements of Thai society for the past 400 years. The present Thai royal family, the Chakri Dynasty, was founded by King Rama I who himself was partly Chinese. His predecessor, King Taksin of Thonburi dynastry, was the son of Chinese immigrant from Guangdong Province and was born with a Chinese name. Nearly all of Thai Chinese identify themselves as being Thai due to the highly successful integration of Chinese communities into Thai society. Descendants of most ennobled Chinese are among the leading Thai families today. In addition, over half of ethnic Thais (the rest are southern Thai who are mostly of Malay descent) are descendants of people who migrated from southern China approximately 1,000 years ago and are directly associated, racially, culturally, and linguistically, with China's modern day ethnic minority group, the Dai people.