An Australian website editor and his reporter colleague faced criminal defamation charges in a Thai court on Tuesday for reporting on Thai naval officers’ alleged involvement in the trafficking of Burmese Rohingya migrants.

Alan Morison, editor of independent news website Phuketwan, and reporter Chutima Sidasathian face up to seven years in jail and thousands of US dollars in fines if found guilty.

Speaking to the Guardian just before he entered court, Morison, 67, called the trial “a vindictive reaction on the part of one or two officers” and said the case – widely condemned by human rights and media freedom groups – has damaged Thailand’s reputation.

“It’s uncharacteristic of the Thai navy, which is an honourable organisation,” he said. “I could have stayed in Australia and not fought this case,” he added. “But I’m afraid nearly 50 years in journalism has told me not to run.”

The court was packed with international media and observers. The Australian embassy had also sent officials to the trial. A video-link was set up to a separate room as the courtroom was too small to accommodate everyone.

The trial will last three days, during which members of the Thai navy will testify, after which the judge will have 30 days to give a verdict.

Morison has closed down his website for the trial. A note on the site says: “Our reporting on vital matters about Phuket and Thailand will come to an end next week and may never resume.”

Rights advocacy group PEN American Center, said the “government of Thailand should refocus its energies on curbing collusion in human rights abuses by members of its own navy, rather than frivolous attempts to camouflage them by shackling the press.”

The defamation claims and charges under the Computer Crime Act, which bans online material considered a threat to national security, relate to a 41-word paragraph from a Reuters news agency report on Rohingya refugees, which was republished in Phuketwan.

Reuters, a massive news organisation of more than 2,600 journalists which won a Pulitzer prize for its reporting on the Rohingya issue, has not been charged.

In May, multiple mass graves and human trafficking camps were discovered along Malaysia’s border with Thailand, further spotlighting the trafficking of Muslim Rohingya from Burma who face persecution at home. In Thailand, their traffickers hold them for ransom in jungle camps.

The Thai navy has denied its officers were involved in human trafficking. But since the charges were made against the two journalists, the Thai government has launched investigations into official complicity into the trafficking trade and a senior military official was arrested.

Reporters Without Borders, an international non-profit group defending media freedoms, said it had sent the head of its Asia-Pacific desk, Benjamin Ismaïl, to observe the trial.

“The trial of these two journalists, who just did their job as news providers, with a great deal of professionalism, poses a great danger to all those independent voices in Thailand who want to use their freedom of expression and information,” Ismaïl said in a statement.

Thailand’s ruling junta, which toppled the government of Yingluck Shinawatra in a coup last May, has stifled the media and banned political gatherings.

The prime minister, Prayuth Chan-ocha, has said he will “probably just execute” any journalist who does not “report the truth”.

The New York-based Committee to Protect Journalists wrote an open letter to Prayuth saying the charges against Morison and Chutima were “intended to discourage other journalists from probing the politically sensitive issue of human trafficking in your country.”