Small pavilion house the Buddha image used in the Royal ploughing Ceremny or the ceremony of the first rice planning. This chapel of a Buddha image called Phra KhantharaRat is used for invoking rain- or rain-making ceremony according to ancient Thai belief of the first rice planting. The Phra Buddhakhanthararat image is enshrined here.


source : Tourist Guide to Thailand book,Thailand-sawasdee.blogspot.com