Concept
Isan or Northeastern Thai (ภาษาอีสาน, ภาษาไทยถิ่นตะวันออกเฉียงเหนือ, ภาษาไทยถิ่นอีสาน, ภาษาไทยอีสาน, ภาษาลาวตะวันตก, ภาษาลาวอีสาน) refers to the local development of the Lao language in Thailand, after the political split of the Lao-speaking world at the Mekong River, with the eastern bank eventually becoming modern Laos and the western bank the Isan region of Thailand (formerly known as Siam prior to 1932), after the conclusion of the Franco-Siamese War of 1893. The language is still referred to as Lao by native speakers. As a descendant of the Lao language, Isan is also a Lao-Phuthai language of the Southwestern branch of Tai languages in the Kra-Dai language family, most closely related to its parent language Lao and 'tribal' Tai languages such as Phuthai and Tai Yo. Isan is officially classified as a dialect of the Thai language by the Thai government; although Central Thai is a closely related Southwestern Tai language, it actually falls within the Sukhothai languages. Central Thai and Lao (including Isan) are mutually intelligible with difficulty, as even though they share over 80% cognate vocabulary, Lao and Isan have a very different tonal pattern, vowel quality, manner of speaking and many very commonly used words that differ from Thai thus hampering inter-comprehension without prior exposure. 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 (1354–1707). After the fall of Lan Xang, the Lao splinter kingdoms became tributary states of Siam. During the late 18th and much of the 19th century, Siamese soldiers looking to weaken the power of the Lao kings carried out forced migrations of Lao from the left to the right bank, now Isan, impressing people for enslavement, corvée projects, the Siamese armies, or developing the dry Khorat Plateau for farming to feed the growing population.