Wat Yai Chaimongkol was originally named Wat Pa Kaew 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 Kaew” that is why this temple was also named Wat Pa Kaew. Then, the impieties of this group have appointed the leader as Somdet Pra Wanrat and is also the right patriarch with the Pra Puttakosajan 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 Kaew 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 Tambol Nongsarai, Supanburi, 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 “Chaimongkol Chedi”. The people called it “Chedi Yai”. After that, it was combined together to “Wat Yai Chaimongkol”. However, it was abandoned after the 2nd fall of Ayuttaya. It was then restored again during the Rattanakosin Kingdom.