The history of Isan (, ) has been determined by its geography, situated as it is on the Korat Plateau between Cambodia, Laos, and Thailand. Occupation of the plateau is attested from prehistory. Dvaravati culture is generally held to have spread into the region from the 6th century, and inscriptions of the following centuries name local rulers across the Mun and Chi basins. Parts of the plateau may have come under Chenla influence, and Angkor later built temples along the routes down to the central plain. The evidence has been read as a network of polities rather than a unified kingdom. Lao settlers moved across the Mekong between the 14th and 16th centuries, and Lan Xang and then Siam drew the region into their spheres.
Isan has been dominated by each of its neighbors in turn, although its relative infertility meant it was more often a battleground than a prize. Rather than being incorporated into the respective empires of each power, the area was divided into mueang ("city-states", ), each paying tribute to one or more powers under the mandala system.
The Thai king Vajiravudh reinvoked the ancient name, designating the northeast sector of the Rattanakosin Kingdom "Isan". The national government claimed that the name "Isan" was derived from Sanskrit Īśāna, a name of Shiva they claimed referred to his rule of the northeast (Sanskrit īśānya).Royal Institute - 1982: อีสาน ๑ The interpretation was meant to fix Isan's identity as the northeast of Thailand rather than as part of the Lao kingdom, from fear that the Lao people would secede. Previously, in the reign of Chulalongkorn in the early 20th century, the area north of Nakhon Ratchasima (Korat) was generally called Hua Mueang Lao (Lao Townships ). The townships to the east were called Khamen Pa Dong (Wilderness Khmer, ). Later, the term Isan came into wide, if unofficial, use as a term for the northeastern region, and khon Isan (Isan people, ) as a general term for the peoples of Isan.
Throughout the 20th century, the Thai government took steps to cement Isan's status as a part of Thailand and to de-emphasize the Lao, Khmer and Kuy origins of its population, a process known as Thaification. Before the central government introduced the Thai alphabet and language in regional schools, the people of Isan wrote in the Lao alphabet, a very similar script that Thai adopted. Most people still speak the Isan language, a dialect of the Lao language, as their first language, and a significant minority in the south speak Northern Khmer. Substantial minorities of Katuic speakers, among them Kuy, Bru and So, also live in the region, and most Isan people are conversant and to some degree literate in Central Thai. The Kuy people, an Austroasiatic people concentrated around the core of what was once the Chenla Kingdom and known as the Khmer Boran "ancient Khmer", are a link to the region's pre-Tai history. From the 1960s the region saw Communist political attacks and a large American military presence, and the government promoted development there as one weapon against Communism. Prehistory Four Homo erectus fossil skull fragments found in northern Thailand's Hat Pudui cave (Ko Kha District, Lampang Province) by Thai paleontologists Somsak Pramankij and Vadhana Subhavanin, were in deposits dating from the mid-Pleistocene era, which was before the Khorat Plateau had uplifted from an extensive plain. Professor Phillip V. Tobias of Johannesburg's University of the Witwatersrand examined the fragments and said: "It seems unavoidable but to conclude that Thailand must have been a highway or crossroads in the movement of hominids — members of the family of man."
Pha Taem cliff paintings alongside the Mekong in Udon Thani Province date to around 1500 BC. They are younger than but similar in composition to the Rock Paintings of Hua Mountain in southern China. Those paintings are attributed to the Luoyue people of what is today the lowland plains of northern Vietnam, especially the marshy, agriculturally rich Red River Delta. The Luoyue are associated with the Bronze Age Đông Sơn culture of mainland Southeast Asia.
The Ban Chiang archaeological site, dating from around 3000 BC to 300 AD, attracted attention in 1966 as seemingly the world's oldest site showing traces of a Bronze Age culture, due to errors in dating. In Fine Arts, the site is remarkable for its pottery; further investigation into ancient skeletal remains raised serious questions about transitions to sedentism and intensified agriculture. The question as to why the site was abandoned until resettled by 19th–century Lao émigrés remains to be settled. The Bronze Age site of Ban Non Wat in the southeast of the plateau is also under investigation (2002–present.)
The settlement record of the plateau for the Iron Age and the early historic centuries has been set out. Small settlements of half a hectare to five hectares lay in marshland and in low-lying stream valleys away from the main rivers, and may have held 250 to 500 people each. Sites on the alluvial plain of the Phimai region ran from one to seventeen hectares, most of them with water-control works. In the Nam Phong watershed the change between about 500 BCE and the turn of the era has been read as a nucleation of communities, perhaps with the adoption of fixed-field wet rice. How far that amounted to political authority is disputed. A hereditary upper chiefly class exercising authority over a unit larger than one settlement has been described. Against that, most research is held to show no more than broad trends toward economic and political centralisation.
The plateau is rich in natural salt. Basal layers of some salt mounds in Buriram and Nakhon Ratchasima provinces lie with water-storage tanks, furnaces and Phimai black pottery, which has been taken to place salt making as early as about 500 BCE. Ironworking is reported from Mun valley sites, among them Noen U-Loke, Ban Don Phlong and Ban Karbuang Nok, as smelting areas, clay-lined furnaces, tuyeres and slag. At Noen U-Loke the furnaces lie in layers of roughly the first five centuries CE, some of them covered with sheets of asbestos. Burials at the site grow markedly richer by about the turn of the era, with bronze and iron ornaments, glass, gold and carnelian and agate beads, and the dead laid in beds of rice. In the Phimai region the same centuries are read as a phase of agricultural intensification. Ploughing, transplanting and simple water control appear between about 600 and 200 BCE, together with the first moats and banks, the earliest iron and a new pottery tradition. Settlement spread from the alluvial plain onto the terraces and uplands. Population pressure is not offered as the cause, since the plain could have supported more people than lived on it. The change is read instead as an answer to an unpredictable climate, with salt, iron and timber drawing settlers into the higher ground. By the end of the period large stretches of floodplain and low terrace had been turned from wild grassland into bunded rice fields. The working of salt, iron-bearing laterite and fuel wood is held to have told on the forest. The settlement record of the Phimai region has been divided into dated phases running from about 1000 BCE to about 1300 CE. Before about 600 BCE the region is known from only five sites, all on the alluvial plain and none visible at the surface, so the count is called much too low and the conclusions tentative. Moated settlement was at its height between about 200 BCE and 300 CE, when more than half the recorded sites were enclosed. For the three centuries after about 300 CE no settlement pattern could be proposed at all, the pottery of that phase not yet being distinguishable from the one before it.
Early history
The region's Early Historic period has been put at about 500 to 800 AD, following a pre-literate Iron Age of about 500 BC to 500 AD. The period is usually described in terms of two poles of influence, the ostensibly independent states of Khmer-Hindu Chenla to the south and Mon-Buddhist Dvaravati to the west, terms that have been called increasingly problematic.
On the study of artefacts, Dvaravati has been taken for the first major civilisation to occupy Isan. Its culture spread into the region and into lowland Laos from the 6th century, with major sites at Mueang Fa Daet in Kalasin Province and in Nakhon Ratchasima Province. The remains of walled and moated towns scattered the region, in the valleys of Chi and Mun Rivers. The enclosures themselves are disputed. Geomorphological work in the upper Mun valley reads some of these features as remnants of old river channels rather than as dug ditches, which weakens the case for a defensive purpose. The remains often show the Buddhist and Hinduist influence, perhaps expanding from the western part or the coastal and the Chao Phraya River basin. In the Phimai region the material culture changed at about the time the first written records appear, on one reading of the excavated sequence. The local Phimai pottery tradition gives way to a grog-tempered, more highly fired and often wheel-turned ware, and incising replaces streak burnishing. Inhumation burial disappears, while urn burials continue and may hold cremated remains rather than bones. The phase that follows, and that precedes the Khmer period, is named the Muang Sema phase, about 600 to 1000. Survey in the region finds the settlement pattern of those centuries contracting. Sites on the alluvial plain and the terraces fall in number, moated sites most of all, and many large settlements appear to have been given up, while the uplands hold steady. The reason is called uncertain. Treating that span of four centuries as one unit is held to be inadequate for the period in which statehood took shape. A finer chronology is called for before the shift from moated settlements to the walled cities of the Khmer state can be followed.
Settlement and religious landscape of the Khorat Plateau
The Khorat Plateau and the middle Mekong, east of the core Dvāravatī centres, appear to have developed outside the Dvāravatī political network as a loose landscape of small fortified and moated settlements. Against the site inventories of Thiva Supajanya and , local traditions have been read as preserving the names of early settlements there, especially the legend of Phadaeng Nang Ai and the Tamnan Fa Daet Song Yang (). Mueang Fa Daet, the first site in northeastern Thailand identified as "Dvāravatī" by H. G. Quaritch Wales, is traditionally attributed to the foundation of Chao Fa Ra-ngum in 621 CE. The same reading cautions against applying "Dvāravatī", "Mon" or even "Buddhist" uncritically to the plateau, whose traditions instead depict largely autonomous muang, some with subordinate settlements and others independent, alongside Buddhist practice, fertility cults and local spirit beliefs influenced by Hindu deities. Any cultural or political distinction between Mon and Khmer in the Northeast has been treated as probably not justified until at least 1000 AD. The settlement evidence has been read to the same effect. The largest early historic sites of the plateau are taken for ceremonial rather than administrative centres, with the societies around them integrated more by shared belief and ritual than by political unification. The data are described as far from adequate to test any of the historical models. Literal readings of the documentary record for the pre-Angkorian kingdoms have largely been abandoned. The alternative models that replaced them are held to outrun what the archaeology can yet test.