Geography
North Thailand is bound by the Salawin (สาละวิน) River in the west and the Maekong in the east. The basins of rivers Ping, Wang, Yom, and Nan, all tributaries of the Chao Phraya River, in the central part run from north to south and are mostly very wide. The basins cut across the mountains of two great ranges, the Road Range in the western part and the Phi Pan Nam in the eastern. Their elevations are generally moderate, a little above 2,000 metres for the highest summits. Although formerly forested, many of these mountains are now denuded.