A criminal defamation case against two journalists in Thailand, including an Australian, is set to begin today, despite calls from the United Nations for the charges to be dropped.

Alan Morison and his Thai colleague Chutima Sidasathian, who run an online news site in Phuket, will hear the criminal charges brought by the Thai navy at a court on the southern resort island.

They could face up to two years' imprisonment for defamation and five years for breaching the Computer Crimes Act, as well as a $3,100 fine.

The complaint relates to an article published by their independent news website Phuketwan in July last year.

The article quoted an investigation by the Reuters news agency, which said some members of the military were involved in trafficking Muslim Rohingya asylum seekers who had fled Myanmar.

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Morison has told Radio Australia's Asia Pacific program that he and Chutima have "done absolutely nothing wrong".

"All we've done is republished one paragraph from the Reuters news agency and in that paragraph a human trafficker is quoted as making some allegations about the military along the coast north of Phuket," he said.

"The Royal Thai Navy isn't specifically mentioned in the paragraph and both Phuketwan and Reuters have gone out of their way to try to make sure that we don't make accusations that we don't have evidence for.

"The whole case really revolves around a very bad translation of the paragraph that we carried in English into Thai.

"Whereas the Royal Thai Navy isn't mentioned in the English version, the translators have managed to insert the Royal Thai Navy three times into the Thai version."

Phuketwan is a small but respected English-language news website based in Phuket. For years it has reported on the plight of Rohingya asylum seekers.

Morison, a one-time Melbourne Age journalist, has told AM he thinks the Thai navy is perhaps trying to wipe out Phuketwan.

"We think they've just gotten tired of our coverage and decided to teach us a lesson," he said.

"We've been exposing what's been happening off Thailand and inside Thailand for the Rohingya boat people who come down looking for sanctuary and find themselves in the arms of human traffickers - they are treated appallingly at every level.

Morison packs up office, prepares for the worst

"[The lawsuit] is a trumped-up charge. It's designed to put Phuketwan out of business - it's as simple as that."

But despite Morison putting on a brave face at the prospect of heading to jail, he has already packed up his Phuket office in preparation for the worst.

"We've been inside Phuket prison several times on different visits, so we know what it's like," he told AM.

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"It's very crowded. There are 300 people to each cell. But at least they have a TV set in those cells now and ceiling fans."

He says he will take the stand later today and as a protest he will refuse to pay bail.

"We stand, not only... by the story, we think this is an iniquitous law and it really shouldn't happen in a democracy that the military sues the media," Morison told AM.

Human Rights Watch in Asia deputy director Phil Robertson has told AM it is "quite unusual" to see a branch of the military suing journalists for defamation.

"Much less using the Computer Crimes Act against them. It's a unique case. I can't really actually think of any other case like it," he said.

"Press freedom in Thailand has been going downhill for quite some time now and I'm quite concerned that this is another indication that... other parts of the government, like for instance the military in this case, will be prepared to try to silence critics using these draconian laws."

Reuters wins Pulitzer prize for Rohingya coverage

Reuters was this week awarded a prestigious Pulitzer prize for journalism for the investigation into the trafficking of Rohingya Muslims.

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Chutima, who has assisted Reuters with its coverage, says at least four Thai media outlets have republished the story, but only Phuketwan is being targeted.

"In the past we have [not had] any bad history with the Royal Thai Navy at all," she told the ABC's The World.

"I feel very frightened about my freedom and media freedom. I feel sad that this thing happened in democracy (sic) in Thailand."

Chutima says she wants Reuters to come forward and speak about the issue of press freedom. Morison is also urging Reuters to defend media freedom in Thailand.

"We were delighted that Reuters won the Pulitzer because of the awareness it creates for the Rohingya issue and we congratulate them," Morison told Asia Pacific.

"But my colleague, Chutima Sidasathian, worked with Reuters in that series and guided Reuters reporters to many of the contacts that she's built up over seven years in Thailand covering the story.

"And the paragraph after all is a Reuters paragraph that we've merely republished.

"It really is time Reuters said something about media freedom in Thailand."

Plight of Rohingya asylum seekers

In December, the United Nations urged Thailand to drop the charges, warning of a "chilling effect" on press freedom.

The stateless Rohingya are considered by the UN to be one of the world's most persecuted minorities. They have long made the perilous journey from Myanmar by boat.

But the numbers fleeing to Thailand increased rapidly after Buddhist-Muslim clashes in 2012 in the western state of Rakhine.

Many are believed to be trying to reach Malaysia.

Rights groups have raised concern about alleged cases of boats being pushed back out to sea after entering Thai waters.

They have also criticised the detention of hundreds of Rohingya in overcrowded facilities while Thailand waits for a third country to offer to take them.

ABC/AFP