Wat Yai Chai Mongkhon (Thai: วัดใหญ่ชัยมงคล) or the “Great Monastery of Auspicious Victory” is located off the City Island in the southeastern area at present Tambon Phai Ling. In the past it bears other names as Wat Pa Kaeo, Wat Chao Phraya Thai and Wat Yai Chaya Mongkhon. A large Chedi of this Wat can be seen from a far distance. People come to play respect and many tourists are seen here especially during weekends.
There are indications that the site was surrounded by a large moat in earlier times. The monastery was accessed before by Khlong (Pak) Khao San, which got its mouth at the new Pa Sak River. There are also traces of an ancient canal east and west of the temple; the latter ran, parallel with Khlong Khao San, also towards the Pa Sak River.