PHNOM PENH (THE PHNOM PENH POST/ASIA NEWS NETWORK) - Emails sent to self-exiled former Cambodian opposition leader Sam Rainsy were among those trotted out during a court's questioning of Australian filmaker James Ricketson on Tuesday (Feb 6).

Ricketson, 68, was arrested in June last year by Cambodian authorities after he flew a drone without a permit over an opposition rally. He was later charged under espionage laws with gathering information for a foreign power that could damage national security, and could be jailed for 10 years if convicted.

He has repeatedly denied the charge, and critics have dismissed it as politically motivated.

Ricketson was questioned for two hours on Tuesday by a judge in a closed Phnom Penh Municipal Court session. The Australian is expected to be questioned again next week, according to his lawyer, Peung Yok Hiep.

Meanwhile, the Australian Broadcasting Corporation (ABC) reported on Wednesday (Feb 7) that Australia's Foreign Minister Julie Bishop has intervened in Ricketson's case.

Ms Bishop has written a letter to her Cambodian counterpart Prak Sokhonn raising concerns about his detention, the ABC understood.

The Australian government has been giving Mr Ricketson consular support, but this was the first time that Ms Bishop had formally made representations to the Cambodian government about his case, it reported.

Ricketson's case has taken place against the backdrop of a broader pre-election crackdown on not only the opposition CNRP, but also on independent media outlets.

Two Radio Free Asia (RFA) journalists have also been arrested on "espionage" charges in recent months after their outlet was forced to shutter its in-country operations.

Meanwhile, dozens of radio frequencies carrying content from RFA and Voice of America were closed in the lead-up to the CNRP's dissolution.

The often critical English-language Cambodia Daily newspaper was forced to close around the same time after being hit with an "exorbitant" tax bill.

In the Phnom Penh court on Tuesday, lawyer Ms Yok Hiep said the judge focused on the content of three emails obtained from Ricketson's seized computer.

The emails were the first pieces of alleged evidence Ricketson has seen during his eight months of pre-trial detention.

In an email to Mr Rainsy from 2013, Ricketson allegedly asks for confirmation as to whether the politician was subject to a new arrest warrant.

At the time, Mr Rainsy was head of the Cambodia National Rescue Party (CNRP), which was forcibly dissolved last November following the September arrest of Mr Rainsy's successor, Kem Sokha, on widely decried accusations of "treason".

Ms Yok Hiep said Ricketson confirmed sending the email to Rainsy.

"It is normal, because he is a journalist, to meet politicians", Ms Yok Hiep said. "He just wanted to confirm with Sam Rainsy, but he was charged with collecting information."

Mr Rainsy, when contacted, said he was unable to locate the email in question on Tuesday, but he defended Ricketson, saying the Australian was simply doing "his work as a journalist" in corresponding with him.

"Emails I received from him were of the kind I received from many other foreign journalists," Mr Rainsy said in an email. "Now James is only a scapegoat and a hostage held by the government to frighten other foreign journalists and deter them from writing critical reports about the Hun Sen regime."

The court also discussed another email, with Ricketson allegedly responding to an email from a foreign friend inquiring about the number of bodyguards assigned to Cambodian Prime Minister Hun Sen, and how many water cannon trucks - used to break up protests - the government had available.

Ms Yok Hiep did not disclose who sent the email, but said Ricketson responded by saying the number of bodyguards was about 10,000.

In a third email discussed in court on Tuesday, an Indian woman asked Ricketson to help a Cambodian film team with a project for an NGO, which Ms Yok Hiep couldn't immediately identify.

Ricketson is being held in the capital's notoriously overcrowded Prey Sar prison, where he was recently moved to a cell containing 140 inmates.