The language is still referred to as the Lao language by native speakers. Isan is officially classified as a dialect of the Thai language by the Thai government, although Thai is a closely related Southwestern Tai language, it falls within the Chiang Saen languages. The Lao language has a long presence in Isan, arriving with migrants fleeing southern China sometime starting the 8th or 10th centuries that followed the river valleys into Southeast Asia.
The region of what is now Laos and Isan was nominally united under the Lao kingdom of Lan Xang , β After the fall of Lan Xang, the Lao splinter kingdoms became tributary states of Siam. It is natively spoken by roughly million people of Isan , although the total population of Isan speakers, including Isan people in other regions of Thailand, and those that speak it as a second language, likely exceeds 22 million. The Lao language in Thailand was preserved due to the Isan region's large population, mountains that separated the region from the rest of the country, conservative culture and ethnic appreciation of their local traditions.
The language was officially banned from being referred to as the Lao language in official Thai documents at the turn of the 20th century. Assimilatory laws of the s that promoted Thai nationalism, Central Thai culture and mandatory use of Standard Thai led to the region's inhabitants largely being bilingual and viewing themselves as Thai citizens and began a diglossic situation.
Standard Thai is the sole language of education, government, national media, public announcements, official notices and public writing, and even in gatherings of all Isan people, if done in an official or public context, are compelled to use the Thai language, reserving Isan as the language of the home, agrarian economy and provincial life.
The Tai Noi was also banned, thus making Isan a spoken language, although an ad hoc system of using Thai script and spelling of cognate words is used in informal communication. Isan is also a more agricultural area and one of the poorest, least developed regions of Thailand, with many Isan people having little education often leaving for Bangkok or other cities and even abroad for work, often employed as labourers, domestics, cooks, taxi drivers, construction and other menial jobs.
