The square pagoda (prathat) at the center of Wat Prathat Si Song Rak was built around the middle of the sixteenth century to, in effect, celebrate a defense pact between the kingdoms of Ayutthaya and Lane Xang (Laos) against their common enemy the Burmese. Dan Sai at the time was on the border between the two kingdoms. A chapel backing onto the pagoda houses a highly revered Buddha image, although you almost can't see it through the cloudy glass doors protecting it.
During the Phi Ta Khon festival, special offerings are left around the base of the pagoda. These consist of pyramidal frames fashioned from split bamboo, to which several hemispherical wax 'flowers' are affixed.