Si Sa Ket is a quiet province on the Cambodia border with Khmer ruins scattered throughout the province.Most notable are the two ruined sanctuaries of Wat Sa Kamphaeng Yai and Noi,dating back to the 10 th century.
However, the most famous Khmer site is actually in Cambodia. Khao Phra Wihan was built over 10 centuries ago and is one of the most spectacular Angkor-period sites. Built as a Hindu temple, it begins in Thailand and rises to 600 metres with the main sanctuary in Cambodia.
After a long period of war, its wonderful craftsmanship,stairways and courts are now being restored. Thi walk to the summit is long and steep, but visitors are sure to be impressed by the size and complexity of its design.
Si Sa Ket has an area of 8,840 square kilometres, comprising the following districts:

Muang Si Sa Ket, Kanthararom, Kantharalak, Khun Han, Phrai Bung, Khukhan, Prang Ku, Uthumphon Phisai, Rasi Salai, Yang Chum Noi, Huai Thap Than, Non Khun, Si Rattana, Wang Hin, Bueng Bun, Nam Kliang, Phu Sing, Benchalak, Muang Chan, Pho Si Suwan and Sila Lat.

link from http://www.tourismthailand.org/destination-guide/sisaket-33-1-1.html