Thailand has denied entry to Cambodian opposition leader Sam Rainsy over concerns he would engage in political campaigning in the neighboring Southeast Asian nation.

Foreign Ministry spokesman Manasavi Sridasopol said Wednesday that Sam Rainsy will not be allowed to enter the country until a general election in Cambodia is over.

Sam Rainsy was scheduled to attend a book launch at the Foreign Correspondents' Club of Thailand, but Manasvi says he was turned away at Bangkok's Suvarnabhumi International Airport on Tuesday.

Sam Rainsy is living in self-imposed exile to avoid 12 years in prison from convictions widely seen as politically motivated.

Thailand has denied visas to several visitors, fearing the trips could upset ties with other countries, including the Dalai Lama's sister and political activists from Indonesia and Vietnam.