"Some of my friends don't stand up and some try to avoid it. It was not the first time I did not stand up. I did it before, but nothing happened until this time."

Chotisak says he has since received hate mail and threatening phone calls, but he insists he did not intend to insult Thailand's revered monarch, King Bhumibol Adulyadej.

Chotisak Oonsong (right) faces up to 15 years in jail if convicted

"There is no law to enforce us to stand at the cinema. If there is no law, it means that it is our choice to choose to stand or not to stand," he said.

"I decided not to stand. It is my right not to stand."

The Thai authorities, however, disagree.

Article 112 of the Thai criminal code outlines one of the most serious charges in Thailand - disrespecting the monarchy.

Strict laws

Thailand is one of the few countries in the world to still prosecute people for criticising the royal family - especially the king, who is held in the highest esteem.

Last year a Swiss man, Oliver Rudolf Jufer, was jailed for 10 years for spraying graffiti on images of the Thai king in the northern city of Chiang Mai.

Chotisak says his case is about defending constitutional rights and freedoms

Also last year, Thai authorities blocked access to YouTube amid a row over a series of videos posted on the site that mocked the king.

The widespread respect the king enjoys across Thailand extends to millions of Thais wearing yellow every Monday to recognise the day of the week on which he was born.

When the monarch was released from hospital last year wearing a pink suit to show his good health, the nation followed suit – triggering a frenzy at clothing stores selling pink shirts.

Thitinan Pongsudhirak, a Thai political analyst, says many Thais have known no other monarch on the throne.

"Thais love and revere His Majesty King Bhumibol Adulyadej who has been on the throne for more than 61 years of a glorious reign and has dedicated his life to good deeds," he said.

Al Jazeera's Bangkok correspondent, Selina Downes, says that even if Chotisak wins his case - which seems unlikely - it is even more unlikely that he will set any sort of precedent.

Most Thais have nothing but the utmost respect for the king, our correspondent says, and revoking the law would be considered the ultimate insult against a man who many believe has dedicated his life to them.