The legal team for convicted Australian spy James Ricketson have submitted a request to the Cambodian monarch, King Norodom Sihamoni, seeking a royal pardon, his lawyer Kong Sam Onn says.
He told AAP on Friday that he submitted the request through Prime Minister Hun Sen's office, which was expected to be forwarded to the monarch following a ministerial review.
The request followed a decision by the Australian film maker not to appeal his conviction and six-year jail term after a marathon trial that was widely criticised by human rights groups and led to calls by Australian politicians for a pardon.
"I submitted the pardon letter to the Prime Minister's Cabinet on Thursday. The cabinet has already asked the Ministry of Justice to review the letter," Kong Sam Onn said.
Ricketson was convicted on August 31 of espionage and crimes endangering Cambodian national security under Article 446 of the National Penal Code.
He was arrested 15 months earlier after flying a drone without a permit over a political rally organised by the now banned opposition Cambodian National Rescue Party (CNRP).
The prosecution alleged Ricketson, 69, was spying for "foreign states" but declined to say which ones or call any witnesses to substantiate the charges.
He vigorously denied the allegations but has since accepted the verdict.
"My father has decided to submit a plea for a king's pardon. The Australian government has indicated to us that they will throw their full support behind this submission," his son Jesse said last week.
"This is no longer a legal issue but a humanitarian one. It is a question of compassion and mercy. My dad is an old man with failing health suffering through incredibly difficult conditions."
Foreign Minister Marise Payne has confirmed the Australian government's support for the application, saying she welcomed the "statement by the Ricketson family that Mr Ricketson intends to formally lodge a petition for clemency".
Under Cambodian law a pardon cannot be issued until the appeals process has been exhausted or dropped. It is normally requested by the convicted with the government then asking King Norodom Sihamoni for a royal approval.
Ricketson has been held in squalid conditions in Prey Sar prison where he has suffered from numerous medical complaints including weight loss, scabies and lice, prompting a transfer to the prison hospital.
"Six years in there will kill him. We need to get him home. I, as his son, on behalf of all of his family and loved ones, am also personally asking for mercy so we can do so," Jesse said.