Surin lies at the center of the southern edge of the Khorat Plateau, a relatively low-lying interior region isolated from the rest of Southeast Asia by surrounding mountain ranges. The south of the province is dominated by the Dongrek mountain range, the escarpment of which demarcates the watershed boundaries and also forms the international border with Cambodia. The mountains, averaging approximately 500m in elevation, are not particularly high but the southward sides are steep cliffs rising rather abruptly from the northern plains of Cambodia significantly hindering any attempt at passing. The main pass in the region is in Surin and cuts through the mountains between Chong Chom and O Smach, Cambodia.
