Thai prosecutors on Monday charged two people already held for more than 70 days with defaming the monarchy in a play, their lawyer said, as lese majeste cases since a May coup continue to mount.

Thailand's revered King Bhumibol Adulyadej, 86, is shielded by tough royal defamation rules under which anyone convicted of insulting the king, queen, heir or regent faces up to 15 years in prison on each count.

Student Patiwat Saraiyaem, 23, and activist Porntip Mankong, 25, were each charged by a Bangkok criminal court with one count of lese majeste linked to an October 2013 performance at a commemoration of a pro-democracy students' uprising.

"After the charges were read, both suspects asked for time to study the charge before give pleas," their lawyer Pawinee Chumsri told AFP, adding they will issue a plea in late December.

The pair were arrested separately in mid-August, several months after the play -- "The Wolf Bride" -- was shown at Bangkok's Thammasat University to mark the 40th anniversary of a famous pro-democracy protest that was crushed by authorities in October 1973.

Patiwat, a final year student at Khon Kaen University, acted in the piece -- which was about a fictional monarchy -- while Porntip co-ordinated the production as well as also playing a small role.

Another man, Jaran Ditapichai -- a prominent supporter of the now toppled government -- told AFP he also faces an arrest warrant for lese majeste for overseeing the events programme.

"It was a modern play that came from several workshops, so there was no script for me to review," Jaran told AFP from Paris, where he is seeking political asylum.

Jaran fled Thailand after he was summoned by the military junta in the days after May's coup.

"When you are charged with lese majeste you can't go back (to Thailand)," he added.

Last month rights group Amnesty International said there had been an "unprecedented" number of people charged with insulting the Thai monarchy since the coup, echoing concerns raised by the United Nations.

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On October 17 a 67-year-old man was charged with insulting the monarchy by scribbling anti-royal comments on a public toilet wall.

In August a 28-year-old musician was sentenced to 15 years in jail for writing insulting Facebook posts about the monarchy between 2010 and 2011.

In another recent case a taxi driver was jailed for two and a half years after his passenger -- a university lecturer who recorded their conversation on a mobile phone -- accused him of expressing anti-royal views, Amnesty said.

The junta says it was forced to grab power after months of anti-government protests.

It has vowed to heal the nation's political divides, expunge the kingdom of corruption and protect the monarchy.

But critics say the lese majeste law has been politicised, noting that many of those charged were linked to the Red Shirts, who are broadly supportive of fugitive former premier Thaksin Shinawatra.

Thaksin, the older brother of ousted prime minister Yingluck Shinawatra, was toppled in a previous coup in 2006 and lives in self-exile to avoid prison for a corruption conviction.

Thailand's long-running political conflict broadly pits a Bangkok-based middle class and royalist elite, backed by parts of the military and judiciary, against rural and working-class voters loyal to Thaksin.