Sdok Kok Thom stone sanctuary is located in Sa Kaeo province on the eastern border between Thailand and Cambodia. It was built in the 11th Century CE as a dedication to the Hindu deity Shiva. The architectural structures and building materials reflect the links with the great Khmer Empire. Overall the laterites and sandstones from which the monuments were constructed are well preserved, after 20 years of anastylosis conservation by Fine Arts Department in 1993-2014. Due to amount of stone, and the considerable size of some stone blocks, questions regarding provenance of Sdok Kok Thom’s building materials have been discussed among archaeologists and scientists for quite some time. In this study, the elemental composition of 224 stone blocks from across the sanctuary was determined using portable XRF. In parallel, three sources of natural sandstones from Sa-pleng, Khao Yak, and Khao Nang Sor were analyzed using the same techniques. The results showed that more than 90% of stone block samples at the Sdok Kok Thom sanctuary have positive correlation with Khao Nang Sor stone samples. This could imply that the majority of Sdok Kok Thom’s building materials were originated from Khao Nang Sor sandstone source, approximately 9 kilometers north of the sanctuary. The information obtained from the study could be further used to better understand not only the origin of the construction materials but also the ancient transportation technology and communication route between Thailand and Cambodia over the last millennium.