In 1357 after Chao Keow and Chao Thai were exhumed and cremated,
King U-Thong converted Pagoda and Wihara into a monastery named "Wat Pa Keow"
for the order of monks who practiced meditation. Then it was called "Wat Chao
Phraya Thai" as it was the residence of Somdej Phrawanarat, who was the right
supreme patriarch, as monks were referred to as Chao Thai during that period. In
1592 when King Naresuan the Great, defeated his enemy in single combat on an
elephant, Somdej Phra Wannarat asked for his forgiveness to the warriors who
could not follow him in combat. He also asked the King to build a big pagoda at
Nongsarai Sub-district in Supanburi and at Wat Chao Phraya Thai to celebrate
his victory to match Phukhao Thong pagoda that was built by King Hongsawadee of
Burma.This pagoda is about 60 meters high, bell-shaped in Ceylonese style named
"Phra Chedi Chai Mongkhon". Normally it is called "Phra Chedi Yai" or Wat Yai Chai
Mongkhon now.