Pa Sak River

The Pa Sak River (, , , Pronunciation] is a river in central Thailand. The river originates in the Phetchabun Mountains, Dan Sai District, Loei Province, and passes through Phetchabun Province as the backbone of the province. It then passes through the eastern part of Lopburi Province and Saraburi Province, until it joins together with the Lopburi River northeast of Ayutthaya Island, before it runs into the Chao Phraya River southeast of Ayutthaya near Phet Fortress. It has a length of and drains a watershed of . The annual discharge is .