Kem Sokha's outspoken daughter Kem Monovithya has broken her silence, calling for the release of the former opposition leader as she marks the fifth anniversary of his arrest.

Sokha, former president of the Supreme Court-dissolved Cambodia National Rescue Party (CNRP), is under ongoing trial on charge of conspiracy with foreign powers to topple the government.

“At midnight of September 2, 2017, [members of] the armed forces raided the residence of my family without presenting an arrest warrant and arrested my father despite his parliamentary immunity as a lawmaker,” she said in a social media post on September 3.

Monovithya went so far as to liken her father's situation to what happened during the Khmer Rouge genocidal regime, when democracy was brought to its knees.

“We democrats are advocating peacefully for the restoration of democracy in Cambodia, by providing freedom to Kem Sokha, to begin with,” she wrote.

Monovithya was of the view that her father’s case is attached to some measures taken by the international community that will continue until the government "opens democratic space".

“Five years have passed and our struggle has not reached our goal, but we have gotten some positive results, such as the release of Kem Sokha on bail,” she wrote.

Sok Eysan, spokesman for the ruling Cambodian People’s Party (CPP), said Monovithya should remain calm as it could backfire otherwise.

“[Monovithya] should let the court case proceed according to legal procedures. It’s like letting the water flow on its natural course ... By keeping talking about it, she may think she is correct, but what she said may amount to putting pressure on the government,” he said.

Eysan said he was fed up with any demands linked to "democratic space".

“I am accustomed to such words. Nowadays, opposition groups keep preaching human rights and democracy. But they are silent when they themselves violate democratic principles. It’s their attempt to put the pressure on the government that has obstructed the progress of this case,” he said.

Sokha’s contentious treason trial has been ongoing with no immediate end in sight. His lawyers have said that the case could only end through a political solution.

Phnom Penh Municipal Court spokesman Plang Sophal said he had not seen Monovithya’s post.

He said he did not understand her appeal for Sokha’s freedom while he is currently not in jail.