Rights group decry the punishment as politically motivated and demand their convictions be quashed.
James Ricketson will soon be freed from a six-year prison term imposed for 'espionage,' sources say.
He says the release was health-related and defends a court order placing Kem Sokha under virtual house arrest.
He says the government is trying to drive a wedge between him and CNRP president Kem Sokha.
Freed from prison in August, Kim Sok was warned by Prime Minister Hun Sen not to criticize his governing of Cambodia.
Hundreds of residents contend that four people arrested for ‘violently occupying’ land are the rightful owners of the property.
They say their concerns were ignored by the Mekong River Commission, which is hosting the meeting.
Rights group, US embassy say recent conditional releases don’t go far enough.
Critics say freeing Kem Sokha on bail is meaningless because the political damage is already done after July's one-party elections.
Diplomats from key countries that denounced the election of lawmakers as illegitimate shun the event.
To avoid international sanctions, Cambodian prime minister Hun Sen must quickly free jailed opposition chief Kem Sokha, Sam Rainsy says.