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
Malaysia–Thailand border the Straits of Malacca and in the Gulf of Thailand/South China Sea. At the western terminus of the land boundary, the 1909 Anglo-Siamese treaty determines the start of the maritime boundary as: The territorial sea boundary agreement between the two countries signed on 24 October 1979 determined the mid-channel point between Langkawi and Tarutao to be at which was made the eastern starting point of the territorial sea boundary. Both countries also have a continental shelf boundary agreement for this segment of their maritime boundary. The agreement, signed 21 December 1978, included Indonesia as a signatory to enable the establishment