Maenam Chao Phraya

The Chao Phraya is a major river in Thailand, with its low alluvial plain forming the centre of the country. It flows through Bangkok and then into the Gulf of Thailand. The Chao Phraya begins at the confluence of the Ping and Nan rivers at Nakhon Sawan (also called Pak Nam Pho) in Nakhon Sawan province. It then flows south for 372 kilometres (231 mi) from the central plains to Bangkok and the Gulf of Thailand.

In Chainat, the river splits into the main course and the Tha Chin river, which then flows parallel to the main river and exits in the Gulf of Thailand about 35 kilometres (22 mi) west of Bangkok in Samut Sakhon. In the low alluvial plain which begins below the Chainat Dam, many small canals (khlong) split off from the main river. The khlong are used for the irrigation of the region's rice paddies.

River Settlements
Cities along the Chao Phraya include Nakhon Sawan, Uthai Thani, Chainat, Singburi, Ang Thong, Ayutthaya, Pathum Thani, Nonthaburi, Bangkok and Samut Prakan, listed from north to south. These cities are among the most historically significant and densely populated settlements of Thailand because of their access to the waterway, with Bangkok alone having a population of over 12 million.

Tributaries
The principal tributaries of the Chao Phraya River are the Pa Sak River, the Sakae Krang River, the Nan River (along with its principal confluent the Yom River), the Ping River (with its principal confluent the Wang River), and the Tha Chin River. Each of these tributaries (and the Chao Phraya itself) is further tributed by additional minor tributaries often referred to as khwae. 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. None of the tributaries of the Chao Phraya extend beyond the nation's borders. The Nan and the Yom River flow nearly parallel from Phitsanulok to Chumsaeng in the north of Nakhon Sawan province. The Wang River enters the Ping River near Sam Ngao district in Tak province.

Chao Phraya watershed
The expanse of the Chao Phraya River and its tributaries, i.e. the Chao Phraya river system, together with the land upon which falling rain drains into these bodies of water, form the Chao Phraya watershed. The Chao Phraya watershed is the largest watershed in Thailand, covering approximately 35% of the nation's land, and draining an area of 157,924 square kilometres (60,975 sq mi).