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
Marikina River Rodriguez are the Puray river (which flows near Avilon Zoo), and the Manga river. Up till this point the river follows a more or less East-West direction until San Jose, Rodriguez, where it takes a sharp North-South turn towards the Municipality of San Mateo, where the Ampid River forms the boundary between Barangays Maly and Ampid. At this point across the River in Quezon City, Calamiong Creek drains Barangay Bagong Silang. Further downstream the Nangka River and its own tributary in the Sapang Labo Creek mark the Boundary between San Mateo and Marikina. Somewhere north of Brgy Tumana in Marikina