A British BBC journalist appeared in a Thai court on Wednesday for the start of a criminal defamation trial brought by a lawyer who featured in an investigation about foreigners being scammed of their retirement homes.

Jonathan Head, the BBC's Southeast Asia correspondent, faces up to five years in jail at the private prosecution on the popular tourist island of Phuket.

Rights groups have said the case exposes how Thailand's broad defamation and computer crime laws scupper investigative journalism and make it difficult to uncover wrongdoing in an endemically corrupt country.

The prosecution was sparked by a 2015 report by Head detailing how two foreign retirees had Phuket properties stolen from them by a network of criminals and corrupt officials. One of the victims, British national Ian Rance, is a joint defendant in the prosecution. Both have pleaded not guilty.

The man bringing the prosecution is Pratuan Thanarak, a local lawyer who featured in the BBC's report looking at how Rance lost $1.2 million worth of properties.

According to the report, Thanarak admitted on tape to certifying Rance's signature without him being present, a move which helped the British retiree's then wife transfer his properties out of his name. She was later convicted and jailed for the scam.

A copy of Thanarak's complaint seen by AFP alleges that the BBC's report caused him to be “defamed, insulted or hated”. It does not detail whether he notarised the signature without Rance being present.

Thanarak declined to speak about the case on the way into court. He warned gathered photographers that he would file a lawsuit against anyone who published images of him. Neither Head nor Rance spoke to reporters on their way into the Phuket court on Wednesday.

In a previous statement, the BBC has said it “stands by its journalism” and that they “intend to clear the name of our correspondent”. Rance and Head face one charge of criminal defamation, which carries up to two years in jail.

Head faces an additional charge under Thailand's Computer Crimes Act, a broadly-worded law which forbids uploading “false data” online and carries a five-year maximum jail penalty.

Unlike most countries where defamation is a civil crime, in Thailand it is a criminal offence. Private citizens can also launch their own prosecutions and they are not forced to pay costs if they lose. Similar cases have been brought in recent years.

Local news site Phuketwan closed down in 2015 after running out of money in its successful bid to defeat a suit brought by Thailand's navy. Andrew Drummond, a British crime reporter, left the country the same year because of multiple cases brought by those he exposed as did British labour rights activist Andy Hall in 2016.