Chao Phraya is a very important river in Thailand. It begins from the north of Thailand from the Ping, Wang, Yom and Nan rivers. Merging to form the estuary at Paknam Pho district, of Nakhon Sawan Province.

It flows southwards through Uthai Thani, Chai Nat, Sing Buri, Ang Thong, Ayutthaya, Pathum Thani, Nonthaburi and Bangkok before flowing into the sea, at the estuary in Samut Prakan Province the surrounding area of the estuary used to be location of the Chao Phraya district, thereby giving the name to the river Chao Phraya.

In the past, the areas in front of Thammasat University that follow the banks of the river stretching downward to Wat Arun Ratchawararam were actually one piece of land, without the river flowing through as it does today.

The former Chao Phraya River’s stream line flowed by passing Bangkok Noi Canal to Taung Chan Area and made a roundabout way to meet Bangkok Yai Canal stream on the present day.

Later during the year 1534-1546 Somdet Phrachairachathirat, the King of Ayutthaya had ordered to dig a short-cut canal in the area of the narrowest isthmus, starting from the mouth of Bangkok Noi Canal, to the mouth of Bangkok Yai Canal, named it Khlong Lat Bangkok (Bangkok short cut canal), which then turned to be the same stream as Chao Phraya River until today.