Kem Sokha will this morning attend a closed-door Appeal Court hearing into his request for release on bail.
An earlier bail plea for the former CNRP leader was rejected by the court in September.
Mr Sokha is currently detained at Trapaing Phlong prison in Tbong Khmum province, awaiting trial on treason charges.
Touch Tharith, deputy secretary-general and spokesman for the Court of Appeal, said Mr Sokha would be brought to attend the hearing today at 7am.
Mr Sokha’s lawyer Pheng Heng confirmed his client would be present at the court.
“They will bring him to the hearing,” he said. “We received the information through his family.”
Mr Sokha’s daughter Kem Monovithya, also a former CNRP official, posted on Twitter that her father’s hearing would take place at 8am today.
The former CNRP president was charged with treason last year over comments made in 2013 video footage from Australia-based CBN news, which showed him saying the US government had been helping him to push for regime change in Cambodia since 1993.
The offence is punishable by 15 to 30 years in jail.
Eight of Mr Sokha’s defence lawyers walked out of the courtroom at his previous bail hearing, after prison officials failed to bring their client to court.
The appeal was intended to challenge Mr Sokha’s arrest and detention, with lawyers making the case his parliamentary immunity had been wrongly breached.
The prison department claimed at the time that security and safety issues could arise if the former CNRP leader was transported from prison to the court for the hearing.
The US Embassy has called on the government to immediately release Mr Sokha, claiming allegations the US helped him push for regime change were made without a shred of serious or credible evidence.
Interior Ministry spokesman Khieu Sopheak said the court and the authorities had made security precautions ahead of Mr Sokha’s appearance at the Appeal Court today.
“We have enough police to defend security,” he said.
The opposition CNRP was dissolved by the Supreme Court in November following Mr Sokha’s arrest.