Sixty-two 'domestic' languages are officially recognized, and international languages spoken in Thailand, primarily by international workers, expatriates and business people, include Burmese, Karen, English, Chinese, Japanese, and Vietnamese, among others.

[2] The following table comprises all 62 ethnolinguistic groups recognized by the Royal Thai Government in the 2011 Country Report to the UN Committee responsible for the International Convention for the Elimination of All Forms of Racial Discrimination, available from the Department of Rights and Liberties Promotion of the Thai Ministry of Justice.

The following table shows all the language families of Northeast Thailand, as recognized in the report which is the source for the national breakdown.

The sole official language of Thailand is Central Thai (Siamese), a vernacular language in Central (including the Bangkok Metropolitan Region), Southwestern, and Eastern Thailand, along with Thai Chinese ethnic enclaves in outer parts of the country such as Hatyai, Bandon, Nangrong, and Mueang Khonkaen.

All languages are partially mutually intelligible with Central Thai, with the degree depending on standard sociolinguistic factors.

[16] The following table shows ethnolinguistic groups in Thailand with equal to or more than 400,000 speakers according to the Royal Thai Government's 2011 Country Report to the Committee Responsible for the International Convention on the Elimination of All Forms of Racial Discrimination (ICERD).

[4] Note that the degree to which language speakers will have shifted in their idiolects towards Central Thai will depend on standard sociolinguistic factors, like age, education, gender, and proximity to an urban center.

2 (Provincial): "The language is used in education, work, mass media, and government within major administrative subdivisions of a nation."

8a (Moribund): "The only remaining active users of the language are members of the grandparent generation and older."

9 (Dormant): "The language serves as a reminder of heritage identity for an ethnic community, but no one has more than symbolic proficiency."

In Thai censuses, the four largest Tai-Kadai languages of Thailand (in order, Central Thai, Isan (majority Lao),[17] Kam Mueang, Pak Tai) are not provided as options for language or ethnic group.

The monolingual education system is generally seen as ineffective, with one-third of teenagers functionally illiterate.