It begins at the confluence of the Ping and Yom river at Nakhon Sawan (also called Pak Nam Pho) in the Nakhon Sawan province. The Yom and its biggest confluent, the Nan river, flow nearly parallel from Phitsanulok till Chumsaeng in the north of Nakhon Sawan province. The biggest confluent of the Ping is the Wang river which enters near Wang Chin.
The Chao Phraya runs from north to south for 370 km from the central plains to Bangkok and the Gulf of Thailand. Other major cities along the river are Uthai Thani, Chainat, Singburi, Ang Thong and Ayutthaya.
On old maps the river is named as Menam or Mae Nam, the Thai word for river. Chao Phraya can be translated as General.