Cities, mountains and rivers of Isan.
The Mekong forms most of the border between Thailand and Laos to the north and east of Isan, while the south of the region borders on Cambodia. The Mekong's main Thai tributary is the Mun River, which rises in the Khao Yai National Park near Nakhon Ratchasima Province and runs east, joining the Mekong in Ubon Ratchathani Province. The other main river in Isan is the Chi River, which flows through central Isan before turning south to meet the Mun in Sisaket Province. The smaller Loei and Songkhram rivers are also tributaries of the Mekong, the former flowing north through Loei Province and the latter flowing east through Udon Thani, Sakon Nakhon, Nakhon Phanom, and Nong Khai Provinces.