Prasat Khao Lon is situated at Ban Charoen Suk, Thappharat Sub-district. The Prasat stands in the compound of Wat Prasat Khao Lon on the summit of Khao Lon, a small hill located at the foot of Khao Sakae Krong. It comprises four prang towers but only the central one remains relatively intact. The other three, two at the front and one at the back, have only the bases remaining. Its characteristics are similar to Prasat Khao Noi which was constructed of bricks on a sandstone base. The top of the Prasat has been broken, while on the sandstone door frame appears an ancient inscription. In the northeastern side of the Prasat lie 2 large ponds connected to the Prasat by an ancient path. There are traces of a village or ancient community in the past surrounding this mountain.
As of June 2019, the principal tower is undergoing renovation with an assessment of its origins better understood but it could be as early as Prasat Khao Noi which dates from the 7th century.

Source: http://www.thailandtriptour.com/sakaeo/prasat-khao-lon-2.html