Australian James Ricketson, 69, was detained in June 2017 while flying a drone over an opposition Cambodia National Rescue Party (CNRP) rally and charged with collecting information that may undermine national defence.
He faces up to 10 years in prison if convicted.
The CNRP was dissolved by court order last year and has been banned from participating in the country’s upcoming elections on July 29.
The political party’s president was detained in September on widely criticised treason charges.
Ricketson’s newly hired attorney, Kong Sam Onn, needed additional time to study some 1,400 pages of case files and build a defence strategy, Ricketson’s son, Jesse Ricketson, said yesterday.
His father remained in the medical ward of Prey Sar prison in the capital Phnom Penh with an undiagnosed chest complaint and other health conditions, Jesse Ricketson said.
In a letter published by the Khmer Times last week, James Ricketson apologised to long-time Prime Minister Hun Sen for previous critical remarks, writing that he realised his past “disrespectful comments” about the government were “disruptive and ill-informed.”
The trial is scheduled to resume on August 16, attorney Peung Yok Hiep said.