Wat Yai Chaimongkhon was originally named Wat Pa Kaeo or Wat Chaoprayathai. It is situated at the east side of Pa Sak River. As the history said, it was assumed that King U Thong built this Temple as the place for the monks who came back from the ordainment in Sri Lanka to stay. This monk group’s name is “Pa Kaeo” that is why this temple was also named Wat Pa Kaeo. Then, the impieties of this group have appointed the leader as Somdet Phra Wannarat and is also the right patriarch with the Phra Puttakosachan as the left patriarch. After that, they changed the name of the temple to “Wat Chaoprayathai” which was assumed that this name came from the reason that King U Thong built this temple at the cremation place of Chao Kaeo Chai Thai or might be the reason that this temple is the dwelling place of the right patriarch which was originally called “Chao Thai”.
This temple also had a bond with King Naraesuan’s reign. In year 1592, when King Naraesuan conquered the war with King Uparat of Myanmar at Tambon Nongsarai, Supan Buri, he built a big chedi as the signal of the conquest. It was not clear whether it was a new chedi or a restoration of an old one. However, it was named “Chaimongkhon Chedi”. The people called it “Chedi Yai”. After that, it was combined together to “Wat Yai Chaimongkhon”. However, it was abandoned after the 2nd fall of Ayutthaya. It was then restored again during the Rattanakosin Kingdom. The interesting thing inside the temple is the chedi and the viharn which was built during King Naraesuan’s Kingdom.
