River systems of Thailand

[1] The Mekong is the only river system in Thailand which drains into the South China Sea.

It then flows from north to south for 372 kilometres (231 mi) from the central plains through Bangkok to the Gulf of Thailand.

In the low alluvial plain which begins below the Chai Nat Dam, many small canals (khlong) split off from the main river.

All of the tributaries, including the lesser khwae, form an extensive tree-like pattern, with branches flowing through nearly every province in central and northern Thailand.

[4] The Nan and the Yom Rivers flow nearly parallel from Phitsanulok to Chumsaeng in the north of Nakhon Sawan Province.

It originates in Kaeng Krachan National Park, Kaeng Krachan District and flows through Tha Yang, Ban Lat, Mueang Phetchaburi and empties into the Bay of Bangkok in Ban Laem District.

The Pran Buri River is in Prachuap Khiri Khan Province, on the Kra Isthmus of the Malay Peninsula.

The Pran Buri River originates in southern part of the Kaeng Krachan National Park, and after 130 kilometres (81 mi) empties into the Gulf of Thailand.

The watershed of the Pran Buri River has an area of about 2,000 square kilometres (770 sq mi).

[3] The Tapi River with its main tributary Phum Duang drain the area of Surat Thani Province.

It is the 11th-longest river in the world, and the 12th-largest by volume (discharging 475 cubic kilometres (114 cu mi) of water annually).

[7] From the Tibetan Plateau it runs through China's Yunnan Province, Myanmar, Thailand, Laos, Cambodia, and Vietnam.

Just above Phnom Penh is the confluence with the Tonle Sap, the main Cambodian tributary.

It then leaves China and meanders through Myanmar (where it is known as the Thanlwin) and Thailand (where it is known as the Salawin, Thai: สาละวิน) on its way to emptying into the Andaman Sea by Mawlamyaing (Moulmien).