Noted for its numerous Khmer style religious temples scattered all over the province, Si Sa Ket is one of the most well-known destinations in northeastern Thailand. It is about 571 kilometers from Bangkok. It borders with Ubon Ratchathani in the east and Democratic Kampuchea in the south.

The province is located in the valley of the Mun river, a tributary of the Mekong. The Dângrêk mountain chain, which forms the border with Cambodia, is in the south of the province.Khao Phra Wihan National Park covers an area of 130 km² of the Dângrêk mountains in the southeast of the province. Established on March 20, 1998, it is named after a ruined Khmer Empire temple Prasat Preah Vihear (anglicised in Thailand as Prasat Khao Phra Wihan), now located in Cambodia, which had been the issue of boundary dispute. The temple faces north and was built to serve the Sisaket region. Earlier maps had shown it as belonging to Thailand.The Thai government ignored the deviation and regarded the temple as belonging to Sisaket province. In the 1950s, newly independent Cambodia protested the Thai "occupation". In 1962 the Thai government agreed to submit the dispute to the International Court of Justice. To their dismay, the court voted 9 to 4 to confirm the 1907 boundary and awarded the temple to Cambodia. Access is principally from the Thai side, as the site is difficult to reach from the Cambodian plains far below. The Cambodian government has expressed interest in building a cable car to carry tourists to the site, though this has yet to happen.