PHNOM PENH, Aug. 16 (Xinhua) -- The trial of jailed Australian filmmaker James Ricketson in a spy case began in Cambodia on Thursday.

Ricketson, 69, was taken to the Phnom Penh Municipal Court in his orange prison uniform for a hearing on the charges of espionage.

He was arrested on June 3, 2017 in Phnom Penh by local authorities when he was flying a camera-toting drone without authorization at the then-opposition Cambodia National Rescue Party rally near the Royal Palace.

He was charged with collecting information which could endanger Cambodia's national security with the intent to pass it on to a foreign entity. Under the charges, he could be jailed between five and 10 years if convicted.

In a July 1 letter to Cambodian Prime Minister Samdech Techo Hun Sen published in the Khmer Times, Ricketson apologized for his mistake.

"I apologize unreservedly and without condition for any distress I may have caused as a result of my ignorance of Cambodian issues. If there is anything I can do to remedy my mistake, please let me know as I only want the best for you and Cambodia," the letter said.

After a two-hour hearing, Phnom Penh Municipal Court presiding judge Seng Leang adjourned the hearing to Aug. 20.