BANGKOK, Aug 13 (Reuters) - Question 8 on Professor Boonsong Chaisingkananont's examination may seem a harmless academic exercise.

"Do you think the monarchy is necessary for Thai society? How should it adapt to a democratic system? Please debate."

But in Thailand, one of the few countries where laws protecting royalty are strictly enforced, it is a taboo question which could land the 46-year-old philosophy lecturer in jail.

Acting on a complaint from a fellow professor at Silpakorn University, police are investigating whether Boonsong insulted King Bhumibol Adulyadej by asking his first-year students to debate the role of the monarchy in exams in 2005 and 2006.

Professor Winai Poonampol said he went to police because Boonsong's teachings posed "a threat to society".

"It should not be biased, teaching only one side like a doctrine," he said.

The accusation is a serious one.

Seen by many Thais as the guiding light, King Bhumibol, the world's longest-reigning monarch who turns 80 in December, receives a near-religious devotion from much of the country's 63 million people.

His portrait adorns offices and homes, and millions of Thais have taken to wearing yellow on Mondays, the colour associated with the king's birthday, to show their respect and loyalty.

One of Boonsong's questions asked: "How does the yellow shirt fever reflect problems in Thai society? Are they problems that need to be tackled? If so, how?"

ABOVE CRITICISM?

Revered as a champion of the poor and a pillar of stability through many crises and coups, only the most delicate portrayal of the King and his family is acceptable -- even though the monarch said publicly in 2005 he was not above criticism.

Since April, Thailand has blocked the on-line video-sharing Web site YouTube for showing video clips mocking the King, and last year it quietly banned "The King Never Smiles", a 500-page biography portraying Bhumibol as "anti-democratic".

A tough lese majeste law imposes jail terms of three to 15 years for anyone who "defames, insults or threatens" the King, Queen, heir apparent or regent.

The most recent conviction, a Swiss man jailed for 10 years in March for defacing pictures of the King, was deported swiftly after King Bhumibol pardoned him.

But too often, critics say, the law has been abused because it allows nearly anyone to level an accusation of disloyalty, compelling police, prosecutors and the courts to act.

"Generally, it's a risk-free action. Anyone can make the charge. You just go to the police," American academic and lese majeste expert David Streckfuss said.

At the height of a political crisis last year, Prime Minister Thaksin Shinawatra and his enemies, who accused him of corruption and abuses of power, hurled lese majeste charges at each other.

His alleged disrespect for the King was cited as one reason for the September coup, which some analysts say was as much about a royalist military and corporate elite removing a nouveau riche businessman who had encroached on their turf.

All lese majeste charges were dropped after he was gone.

Boonsong has not been charged, but police have interviewed students and other faculty members at the leafy campus in Nakhon Pathom on the outskirts of Bangkok.

"We are collecting information," Police Colonel Passakorn Klanwan said. "We are looking at the intent of his teachings".

ECHOES OF MCCARTHY

Insisting he did nothing wrong, Boonsong has refused to hand over the marked exam papers, saying it would violate his students' rights and could expose them to allegations of lese majeste.

"This is like McCarthyism," the bespectacled professor with shoulder-length hair told Reuters, referring to the 1950s anti-communist witchhunts in the United States.

"I think it's important for students to be able to analyse and criticise. They must have a deep understanding of any important institution in Thai society and this includes the monarchy," he said.

More than 500 academics and activists have signed a petition (www.petitiononline.com/4bs2007/petition.html) denouncing the case as a grave threat to academic freedom.

"It bodes ill for Thailand at a bad time for the country, when there are strenuous efforts to roll back all sorts of modern thinking and institutions in favour of those that serve only the interests of its elite," said Basil Fernando of the Asian Human Rights Commission.

The case has unnerved university officials who said they warned Boonsong he was playing with fire.

"In this country, this kind of thing is against the law," said acting Arts Faculty dean Maneepin Phronsuthirak. "If he wants to ask these questions he should go and live in England or Australia or somewhere where it is not against the law.

"What happens to my students if they ask the same questions to people outside the class?"

An informal survey of students suggests the campus is far from becoming a hotbed of republicanism.

"It's only an academic matter, not lese majeste," third-year student Pongpat Manachaisak said.

Sutasinee Akkapanyapak also disagreed with the case.

"Yes, we can criticise. The King said we can criticise but we have to rely on logic. But most people don't dare to because there is barrier to talk about such things," she said.

With the King's prestige at its zenith and a royalist government installed after the coup, some Thais say now is the time to reform or repeal the law altogether.

Sulak Sivaraksa, a social critic who faced lese majeste charges in the early 1990s and under Thaksin, said abuse of the law undermines the monarchy, which is invoked frequently in politics despite the King's officially non-political status.

"If you are really respecting the King, the best present for his 80th birthday would be to withdraw this law," he said.

But others say tinkering is unlikely, especially given that the generals who ousted Thaksin have gone out of their way to wrap themselves and their actions in the royal flag.

During the coup, soldiers tied yellow ribbons to their rifles. Billboards urging a "Yes" vote in an August 19 referendum on a new constitution make an explicit link: "Love the King. Care about the King. Vote in a referendum. Accept the 2007 draft charter".

In the current climate, perhaps it's no surprise Boonsong has yet to decide if question 8 will appear on his exam this year.

"I am not a royalist and I am not an anti-royalist. I am a free mind. I just want an open society," he said.