The Northeast consists of the Khorat Plateau, bordered to the East by the Mekong River. It comprises several small river basins, which drain into the two principal rivers Chi and Mun, and through these rivers flow into the Mekong River. This region is the center for produce rubber and cultivation of other tropical crops (Food and Agriculture Organization, 2011).
The Chi River (Thai: แม่น้ำชี, RTGS: Maenam Chi, pronounced [mɛ̂ːnáːm t͡ɕʰīː]) is the longest river flowing wholly within Thailand. It is 765 kilometres (475 mi) long but carries less water than the second longest river, the Mun. The name of the river is “Mae Si” ([sīː]) in the Isan and Lao languages of the region, being transliterated as “Chi” in Bangkok-Thai. In wet seasons there are often flash floods in the floodplain of the Chi River basin.The river rises in the Phetchabun mountains, then runs east through the central Isan provinces of Chaiyaphum, Khon Kaen, and Maha Sarakham, then turns south in Roi Et, runs through Yasothon and joins the Mun in the Kanthararom district of Sisaket Province. The river carries approximately 9.3 cubic kilometres (2.2 cu mi) of water per annum.