O Smach is a small Cambodian town on the Thai border in Samraong Municipality of Oddar Meanchey Province. Until 1999, there were intermittent battles, and the area was unsafe as the last remaining Khmer Rouge still had control of nearby Anlong Veng. In 2003, an international border crossing was opened between O Smach and the adjacent town of Chong Chom in Thailand's Surin Province. There has since opened a strip of casinos between the Cambodian and Thai passport control counters, enabling Thais to gamble in Cambodia without needing to go through Cambodian immigration. Gambling is illegal in Thailand and gambling in Cambodia is legal only for foreign passport holders. O Smach is at the northern terminus of Road 68 which turns north off National Highway 6 at Kravanh in Siem Reap Province.