The compound was actually located within the Royal Palace grounds. There were no residing monks, and the temple was used for royal ceremonies and for storing royal relics. The three chedis are believed to keep the ashes of three Kings : King Trailok, King Borom Ratchathirat III, and King Rama Thibodi II, as well as Buddha relics.
The Viharn at Wat Phra Si Sanphet was build in 1499 by King Rama Thibodi II. A large Buddha image was housed inside the viharn. Almost 200 kilo of gold was used to cover the image, which was given the name 'Phra Si Sanphet'. When the Burmese sacked Ayutthaya in A.D. 1767 the gold was removed by the enemy. The remains of the Buddha image were later moved to Wat Pho in Bangkok during the reign of Rama I.