The Khorat Plateau also Korat Plateau, is a plateau in the northeastern (Isan) region of Thailand, named for the short form of Nakhon Ratchasima, an historical stronghold controlling access to and from the plateau.
The average elevation is 200 m and it covers an area of about 155,000 km². The saucer-shaped plateau is divided by a range of hills called the Phu Phan mountains into two basins: the northern Sakhon Nakhon Basin, and the southern Khorat Basin. The plateau is tilted towards the south-east, and drained by the Mun and Chi rivers, tributaries to the Mekong that forms the north eastern boundary of the area. It is separated from Central Thailand by the Phetchabun mountain range and the Dong Phaya Yen mountains in the west, the Sankamphaeng Range in the southwest and by the Dongrek mountains in the south, all of which historically made access to the plateau difficult.
These together with the Truong Son Range in the north-east catch a lot of the rainfall, so the South-West monsoon has much lower intensity then in other regions—the mean annual rainfall in Nakhon Ratchasima is about 1150 mm, compared with 1500 mm in Central Thailand. The difference between dry and wet season is much stronger, which makes the area less fertile for rice. The portion known as Tung Kula Rong Hai was once exceptionally arid.
The plateau uplifted from an extensive plain composed of remnants of the Cimmerian microcontinent, and terranes such as the Shan–Thai Terrane, either late in the Pleistocene or early in the Holocene Epoch, approximately Year 1 of the Holocene calendar. Much of the surface of the plateau was once classified as laterite, and layers that can easily be cut into brick-shaped blocks are still so called, but the classification of soils as various types of oxisols is more useful for agriculture. Oxisols of the type called rhodic ferralsols, or Yasothon soils, formed under humid tropical conditions in the early Tertiary. When portions of the plain uplifted as a plateau, these relict soils, characterized by a bright red color, wound up on uplands in a great semicircle around the southern rim. These soils overlie associated gravel horizons cleared of sand by field termites, in a prolonged and still on-going process of bioturbation. Xanthic ferralsols of the Khorat and Udon Series, characterized by a pale yellow to brown color, developed in midlands in processes still under investigation; as are those forming lowland soils resembling European brown soils.
Many of the Prehistoric Thailand sites are sited on the plateau, with some bronze relics of the Dong Son culture having been found. The World Heritage Ban Chiang archeological site, discovered in 1966, yielded evidence of bronze making beginning circa 2000 BC, which lacks evidence of weaponry so often associated with the Bronze Age in Europe and the rest of the world. The site appears to have once been part of a broader culture, until abandoned circa 200 AD, not resettled until the early 19th century. None Nok Tha in the Phu Wiang District of Khon Kaen yielded evidence of an Iron Age settlement dating from 1420 to 50 BC.
The region was once under the suzerainty of the Dvaravati, and later under that of the Khmer Empire, and is dotted with the ruins of Khmer resthouses located about 15 miles, or a day's walk, apart, along Khmer highways. The chapels were not just places of rest, but also hospices and libraries, and typically included a baray (pond.)
Due to scarcity of information from the periods known as the Dark ages of Cambodia, the plateau seems to have been largely depopulated. In 1718, the first Lao muang in the Chi valley — and indeed anywhere in the interior of the Khorat Plateau — was founded at Suwannaphum District in present-day Roi Et Province by an official in the service of King Nokasad of the Kingdom of Champasak.
- Bunopas, Sangad; Vella, Paul (17–24 November 1992). Geotectonics and Geologic Evolution of Thailand. Bangkok: National Conference on Geologic Resources of Thailand. p. 224. "...latest Pleistocene early to the Recent regional uplifting must have occurred."
- Lofjle & Kubiniok, Landform development and bioturbation on the Khorat plateau, Northeast Thailand, Nat.Hist.Bull.Siam Soc. (56), 1996 
- K. Kris Hirst. "Ban Chiang, Thailand Bronze Age Village and Cemetery". About.com. Retrieved 28 Dec 2010.
- "Isaan heartland". Thailand's ancient civilizations. Your Guide to Thai Culture. Retrieved 4 May 2011. "Thailand: Traits and Treasures, National Identity Board, ©2005 by Office of The Permanent Secretary, The Prime Minister’s Office, ISBN 974-9771-52-4"
- Brow, James (1976), "Population, land and structural change in Sri Lanka and Thailand", Contributions to Asian studies (Kogan Page) (issue 9): 47, ISBN 90-04-04529-5
- Khorat Plateau: A selection of articles related to Khorat Plateau from Global Oneness.
- Northern Khorat Plateau moist deciduous forests