Two journalists are on trial in the southern Thai island of Phuket for allegedly defaming the Thai navy.
Their charges stem from a July 2013 online article which included a paragraph, originally published by Reuters, on human trafficking.
Alan Morison and Chutima Sidasathian of website Phuketwan, who pleaded not guilty, face up to seven years in jail.
Reuters quoted an unnamed smuggler that Thai naval forces made money from turning a blind eye to trafficking.
Reuters has since won a Pulitzer Prize for its reporting on the Rohingya which included that particular article. The wire agency does not face any charges.
The trial opened with a navy captain testifying he filed the defamation case on behalf of the navy, a lawyer representing the journalists told AFP news agency.
“He also confirmed that the Phuketwan quotes were lifted from [the] Reuters article,” the lawyer was quoted as saying.
The BBC’s Jonah Fisher says that despite its small size, Phuketwan has a well-earned reputation for reporting on the smuggling and abuse of Rohingya, who come from Myanmar (also known as Burma).
In the last year it has become apparent that some Thai officials – although not specifically the navy – have been making money from people smuggling, says our correspondent.
The Thai government has since embarked on a crackdown with dozens arrested, including officials and policemen.
Rohingya Muslims who face persecution in Myanmar have been fleeing the country in recent years. Many of them head to Muslim-dominated Malaysia or Indonesia through Thailand, often using people smugglers, but many also end up being trafficked.
Mr Morison, a 67-year-old Australian is the editor of the website and Ms Chutima, a 34-year-old Thai citizen, is a reporter. They have been charged with defamation, which can be considered a criminal offence in Thailand.
They also face charges for breaching the Computer Crimes Act.
Rights group Reporters without Borders has condemned the trial calling the act “a draconian 2007 law that gives the authorities a great deal of leeway to gag online critics and arrest journalists and bloggers for political reasons”.
Human Rights Watch’s Phil Robertson said that the trial was “a clear indicator of how far and fast the environment for free expression has deteriorated [in Thailand] under military rule.”
Several rights groups have sent an open letter to Thai PM Prayuth Chan-ocha calling for charges to be dropped.
“We’re seriously concerned, but the principles are pretty clear… the freedom of the media is an essential part of democracy everywhere,” Mr Morison told the BBC earlier on Tuesday.
The Bangkok Post reported that the navy had earlier offered to withdraw the libel case if the two apologised, but they declined as they believed they did no wrong.
“We have always said that, because the paragraph was written by Reuters’ journalists, not us, that Reuters should be asked to apologise. When Reuters apologises, we will consider whether we should too,” Mr Morison was quoted as saying.