Two journalists, including an Australian editor, face jail Tuesday as a Thai court is to decide whether they are guilty of defamation over a report implicating the kingdom's navy in human trafficking.

The trial has sparked widespread condemnation from human rights groups and the UN.

It comes after the region's grim people-smuggling trade was dramatically laid bare this year when migrants were abandoned at sea and in jungle death camps by traffickers following a Thai crackdown, a crisis that eventually forced Southeast Asian governments to respond.

The charges against Alan Morison and his Thai colleague Chutima Sidasathian, of the Phuketwan news website, relate to a July 2013 article quoting an investigation by the Reuters news agency which said some Thai navy members were involved in trafficking Rohingya Muslims fleeing Myanmar.

The navy sued for Phuketwan for defamation in response to their article.

The pair could face up to two years in jail for criminal defamation and five years for breaching the Computer Crimes Act if they are found guilty.

Reuters has not been charged over its reporting -- part of a series honoured with a Pulitzer Prize last year -- and rights groups have accused the navy of trying to muzzle the smaller Phuket-based English-language media outlet.

Phuket Provincial Court is due to deliver its verdict Tuesday morning.

Speaking to AFP ahead of the verdict Chutima said she was resigned to her fate.

"Everything is out of our control now," she said.

"I'm just getting ready, if it's the worst outcome we will end up in jail."

She described the trial as "very sad" adding "the authorities can cover up problems but you can't cover up everything".

Southern Thailand has long been known as a nexus for lucrative and largely unchecked smuggling networks through which persecuted Rohingya Muslims in Buddhist-majority Myanmar, and Bangladeshi economic migrants, amongst others, would pass on their way to Malaysia.

Officials have long been accused by human rights groups of turning both a blind eye to, and complicity in, the trade.

A crackdown in May led to the unravelling of vast people-smuggling networks.

In July Thai prosecutors announced that 72 people have been indicted, including local officials and a senior army general.

However no other military figures have been arrested, something that has raised eyebrows among rights groups and observers who say it is unlikely such an influential officer would have acted alone.

Last month -- for the second year in a row -- Thailand was placed by the United States at the bottom tier of its ranking of countries failing to tackle human trafficking alongside nations like Iran, Libya, North Korea and Syria.

The current crackdown came after the reporting period of the State Department's latest "Trafficking in Persons" report ended and Prime Minister Prayut Chan-O-Cha has expressed hopes his country will be upgraded next year.