River systems of Thailand divides into two major branches, the " Tiền Giang" (Front River) and "Hậu Giang" (Back River). These in turn enter the South China Sea through nine estuaries. The following are the principal tributaries of Mekong River which flow through Thailand (tributaries entirely outside the Thai border not shown). The Mekong drains a considerable portion of northeast Thailand. In terms of Thai territory drained, it is second only to the Chao Phraya system. The Salawin River rises in Tibet (Tibetan: རྒྱལ་མོ་རྔུལ་ཆུ།) after which it flows through Yunnan, where it is known as the "Nujiang" River (), although either name can be
Burma Plate Ma) further faulting developed and the Burma and Sunda microplates began to "break off" from the larger Eurasian plate. After a further series of transform faulting, and the continuing subduction of the India Plate beneath the Burma plate, backarc spreading saw the formation of the marginal basin and seafloor spreading centre which would become the Andaman Sea, a process well-underway by the mid-Pliocene (3–4 Ma). On December 26, 2004, a large portion of the boundary between the Burma Plate and the Indian Plate slipped, causing the 2004 Indian Ocean earthquake and tsunami. This megathrust earthquake had an estimated moment magnitude