Ricketson has been in pre-trial detention in the harsh Prey Sar prison since June; he was arrested after flying a drone over a rally on Phnom Penh's riverfront staged by the opposition Cambodian National Rescue Party and accused of spying against the government - a claim dismissed as ludicrous by supporters of the Australian filmmaker.

The government in Cambodia has been examining his links to the opposition party; strong man leader Hun Sen has accused the party of attempting to overthrow in government, in cahoots with the United States - a suggestion that has been strongly denied.

In a searing account of his time in jail published by Fairfax Media on Tuesday, Ricketson described the bleak conditions he is enduring, sharing a cell with 146 other people with limited access to water and in unsanitary conditions.

"The smell of urine is overpowering ... between 5 pm and 9 pm it is not at all unusual to find, in horror, 10 men bathing themselves with ladles of water while others wash dishes or pee in the crude trench urinal, or use the squat toilet," according to Ricketson.

"Inmates are packed into the cell like sardines, if you can imagine three people sleeping in a single bed you will get some idea of what it is like. Men must sleep with their arms around each other like lovers, legs over torsos, heads within inches of each other."

But a letter to the 68-year-old detainee from the Australian ambassador to Cambodia, Angela Corcoran - obtained by Fairfax Media - reveals Ricketson will not receive any additional assitance.

Corcoran delivers a bland reminder to Ricketson in the letter, dated February 16, that "prison conditions and management vary from country to country and prison to prison" and that local laws and penalties apply overseas.

She states that Ricketson has received the same level of consular assistance as other Australians jailed overseas and "you should have realistic expectations about the extent and type of assistance that DFAT can provide".

"The legal aspects of your case are a matter for you, and your legal representative, who is best placed to pursue your legal issues within the Cambodian legal system. It is not the role of Embassy officials to ascertain the legality of your situation or determine your innocence or otherwise".

There has been mounting pressure for Australian authorities to  intervene more directly to secure the Ricketson's release;  Foreign Minister Julie Bishop has contacted her counterpart, HE Prak Sokhonn, about the matter.

In a statement, Ms Bishop's office declined to comment  on what further efforts were being made on Ricketson's behalf, due to privacy obligations.

Since his arrest on June 3, 2017, Australian officials have visited Ricketson in prison to check on his health 15 times, assisted with medical treatment and spoken with his family and legal representatives.

The maximum period Ricketson can be held before formal charges must be laid is 18 months.

Do you know more? Email: jmassola@fairfaxmedia.com.au Wickr: jamesmassola