The topography of Sisaket features highlands sloping north until the Moon River, basin plains in the north, highlands close to the Phanom Dong Rak Mountain Ranges in the south. The province is geographically divided into two parts, the north and the south, by the Moon River which flows through Amphur Rasri Salai, Amphur Muang Sisaket, Amphur Kanthararom and Amphur Yang Chum Noi. In the northern part lie grassy fields, while the southern part comprises mountainous forests in Amphur Kantharalak, Amphur Khun Han, Amphur Khukhan with the Phanom Dong Rak Mountain Ranges acting as a 85-km borderline between Thailand an Cambodia. Apart from the Moon River, Sisaket is blessed with mountain streams originating from the Phanom Dong Rak Mountain Ranges and flowing into the Moon River, such as Huai (stream) Samran, Huai Nua, Huai Khayung, Huai Tha and Huai Thab Than.