Thai language

Thai, also called Central Thai or historically Siamese, is a Tai language within the Kra–Dai family. It serves as the sole official language of Thailand and is spoken by the Central Thai, Mon, Lao Wiang, and Phuan peoples in central Thailand, as well as by most Thai Chinese communities across the country. Among Thailand’s more than 60 languages, Thai has the highest number of native and total speakers. More than half of its vocabulary comes from or was borrowed from Pali, Sanskrit, Mon, and Old Khmer. The language is tonal and analytic, featuring a complex writing system and a set of relational markers. Spoken Thai varies based on factors like age, gender, class, location, and urban versus rural settings, and it is partly mutually intelligible with Lao, Isan, and certain other Thai dialects. These related languages use slightly different scripts but are linguistically similar, forming a dialect continuum.

As of 2024, over 70 million people in Thailand speak Thai. Many residents in the northern (Lanna), southern (Tai), and northeastern (Isan) regions are bilingual, speaking both Central Thai and their local dialects, since Central Thai dominates television, education, news, and media. Recent research indicates that speakers of Northern Thai (also called Phasa Mueang or Kham Mueang) have dwindled; most people in northern Thailand now use Standard Thai, often only adding a "Kham Mueang" accent to their speech. Standard Thai is based on the educated register of Central Thai speakers and ethnic minorities living around the Bangkok metropolitan area.

Thailand also hosts other related Tai languages. While most linguists view these as distinct but related languages, native speakers often consider them regional variants or dialects of "Thai," or "different kinds of Thai." From the mid-to-late Ayutthaya period onward, Thai gradually became a second language among minority ethnic groups, and today most ethnic minorities are bilingual, speaking Thai alongside their native language.

**Classification**

Standard Thai belongs to the Chiang Saen group of languages, which also includes Northern Thai, Southern Thai, and several smaller languages. Together with Northwestern Tai and Lao-Phutai, these form the Southwestern branch of Tai languages. The Tai languages are part of the Kra–Dai family, which covers many indigenous languages spoken from Hainan and Guangxi, through Laos and northern Vietnam, to the Cambodian border. Standard Thai is the main language of education and government across Thailand, based on the central Thai dialect and written in the Thai script.

**History**

Thai has undergone several historical sound changes, especially from Old Thai to modern Thai. The writing system has existed for about eight centuries, and many changes—particularly in consonants and tones—are still visible in today’s orthography.

**Early spread**

A Chinese source from the Ming dynasty, the *Yingya Shenglan* (1405–1433), reports that Ma Huan described the language of the Xiānluó (Ayutthaya Kingdom) as somewhat resembling the local patois of Guangdong. Ayutthaya, Thailand’s capital from 1351 to 1767, was originally a bilingual society speaking Thai and Khmer. This bilingualism was likely reinforced by the large number of Khmer-speaking captives taken from Angkor Thom after Thai victories in 1369, 1388, and 1431. By the late Ayutthaya period, a language shift occurred: Khmer fell out of use, and descendants of bilingual speakers—both Thai and Khmer—adopted Thai exclusively. During this shift, many Khmer elements entered Thai, permeating all aspects of the language. The Thai of the late Ayutthaya period, which later became Ratanakosin or Bangkok Thai, was a thorough mixture of Thai and Khmer, with more Khmer words in use than Tai cognates. Khmer grammatical rules were actively used to create new disyllabic and polysyllabic words and phrases, and Khmer expressions, sayings, and proverbs were transferred into Thai. The Thais also borrowed royal vocabulary and rules from Khmer to expand their lexicon, later developing this royal vocabulary based on their own environment. Thai and Pali (from Theravada Buddhism) were added as well. An examination of Ayutthaya *Rajasap* shows that Thai, Khmer, and Khmero-Indic worked closely together in both formulaic expressions and everyday speech. Khmero-Indic can be grouped with Khmer, since Indic elements were first adapted into the Khmer system before being borrowed into Thai.

**Old Thai**

Old Thai had a three-way tone distinction on "live syllables" (those not ending in a stop), with no tone distinction on "dead syllables" (those ending in a stop, such as /p/, /t/, /k/, or the glottal stop that closes syllables ending in a short vowel). There was a two-way voiced versus voiceless distinction for all fricative and sonorant consonants, and up to a four-way distinction for stops and affricates. The maximum four-way occurred in labials (/p pʰ b ʔb/) and denti-alveolars (/t tʰ d ʔd/); velars (/k kʰ ɡ/) and palatals (/tɕ tɕʰ dʑ/) had a three-way distinction, with the glottalized series also present.