Isaan (Isaan/Thai: อีสาน) (also written as Isan, Isarn, Issan, or Esarn) is the northeast region of Thailand. It is located on the Khorat Plateau, bordered by the Mekong River (along the border with Laos) to the north and east, by Cambodia to the southeast and the Prachinburi mountains south of Nakhon Ratchasima. To the west it is separated from Northern and Central Thailand by the Phetchabun mountain range.

From the beginning of the 20th century this region in northeastern Thailand was officially named as Isaan, a term adopted from Sanskrit Ishan that means “north east direction.” The term "Isaan" was originally derived from Isanapura, capital of the Chenla kingdom. The Lao-speaking people from this region, who comprise a majority of the population, distinguish themselves not only from the Lao of Laos but in addition also the central Thai by calling themselves later as Khon Isan, or Thai Isan. The Khmer and Kuy (Suai) who live in the southern part of the northeast region of Thailand communicated in languages and follow customs that are more similar to Cambodia than to the tradition of either the Thai people or the Lao people.[

Agriculture is the main economic activity, but due to the socio-economic conditions and hot, dry climate, output lags behind that of other parts of the country. Isaan is Thailand's poorest region Thailand.

The main language of the region is Isaan, of which is a dialect of the Lao language. As a dialect of Lao, but written in the Thai alphabet, Isaan is among the Chiang Seng and Lao-Phutai languages, which are members of the Tai languages of the Kradai language family. Thai is also spoken, with regional accents, by almost everyone. Khmer (the language of Cambodia) is widely spoken in regions near the Cambodian border (Buriram, Surin, and Sisaket). Most of the population is of Lao origin, but the region's incorporation into the modern Thai state has been largely successful.

Prominent aspects of the culture of Isan include the indigenous form of folk music, called mor lam (Thai: หมอลำ), Muay Thai (Thai: มวยไทย) boxing, cock fighting, and celebratory processions (Thai: กระบวน). Isan food, in which sticky rice (Thai: ข้าวเหนียว, khao niao) and chiles are prominent, is sufficiently distinct from Thai cuisine that it is considered unique. Sticky rice is a staple of Thai Northeastern cuisine, and it accompanies meals frequently.

(Source: Wikipedia)