Advocates for the Khmer Kampuchea Krom ethnic group expressed concern Wednesday following the announcement by Vietnam it would try defrocked monk Tim Sakhorn.
Tim Sakhorn has been in Vietnamese custody since July, when he was arrested for allegedly traveling without proper documentation.
"After the investigation is completed, he will be brought to trial, but I don't know the date yet," Trinh Ba Cam, a spokesman for the Vietnamese Embassy in Phnom Penh, said.
Rights groups and family members of Tim Sakhorn, the former head of a Cambodian pagoda, say he is not a Vietnamese resident, and they worry he will not receive a fair trial.
Cambodian authorities have accused Tim Sakhorn of stirring foment between the two countries.
In a statement Wednesday, the Khmer Kampuchea Krom Federation called the trial an act of political and racial revenge.
Ang Chanrith, director of the Khmer Kampuchea Krom Human Rights Organization, said Vietnamese authorities fabricated evidence against Tim Sakhorn.
Witnesses say Tim Sakhorn was stripped his of his monk title days before he was forced into a car by plainclothes authorities. His whereabouts were unknown for weeks before Vietnam claimed to have arrested him.
Thach Setha, executive director of the Khmer Kampuchea Krom Community, said a trial of Tim Sakhorn would reflect Hanoi's continued influence over the Cambodian government, a long-standing claim of Khmer Krom advocacy groups.
Government spokesman Khieu Kanharith could not be reached for comment Wednesday.
Sam Rainsy Party lawmaker Son Chhay said he would lead a delegation to the Khmer Krom area later this month to evaluate the living conditions of the minority group there.