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.
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The average elevation is 200 m and it covers an area of about 155,000 km². The saucer-shaped plateau is tilted towards the south-east, and is drained by the Mun and Chi rivers, tributaries to the Mekong, the north eastern boundary of the area. It is separated from Central Thailand by the Phetchabun mountain range and the Sankamphaeng Range, the southern prolongation of the Dong Phaya Yen mountains; and from Cambodia by the Dongrek mountains to the south, all of which make 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[1], 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.[2]
Many of the Prehistoric Thailand sites are sited on the plateau. 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.[3] 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.)[4]