* King has been in hospital since September

* Active in previous crises, he is silent this time

* Role of monarchy, succession topics in current turmoil

By Bill Tarrant

BANGKOK, May 21 Revered King Bhumibol Adulyadej, the only monarch most Thais have ever known and Thailand's unifying father figure, has remained silent as political mayhem unlike anything seen before in the kingdom unfolded this week.

The 82-year-old king, in hospital since September and undergoing physical therapy after a bout with pneumonia, according to the palace, has defused previous crises in his 63-year reign.

But not this time.

Thailand's fundamental divide between the disenfranchised poor and what they call an "establishment elite" represents a collapse of a traditional order in Thailand at a time when people have begun to broach the hitherto taboo topic of successsion.

"It could be difficult for the king to intervene without appearing to favour one side or the other, and thus potentially compromising his authority as a parental figure dedicated to the well-being of all Thai people," said Danny Richards, analyst at the Economist Intelligence Unit.

Worse would be if a royal initiative failed to stop the violence, Richards said.

Thailand's severe lese majeste laws forbid people to say or write anything publicly critical of the king, regarded as almost divine in the traditional Thai Buddhist culture.

Crown Prince Maha Vajiralongkorn does not command the same devotion his father does, and some from the "establishment elite" think it is time to face the succession question.

"We should be brave enough to go through all of this and even talk about the taboo subject of monarchy," Foreign Minister Kasit Piromya said at a seminar last month at Johns Hopkins University School of Advanced International Studies in Washington.

"I think we have to talk about the institution of the monarchy, how would it have to reform itself to the modern globalised world," he added in remarks from which the government later distanced itself. "Let's have a discussion: What type of democratic society would we like to be?"

UNPRECEDENTED CRITICISM

The concern comes at a time of unprecedented criticism of the king's advisers, known as the privy council.

Anti-government "red shirt" protesters accuse Privy Councillor Prem Tinsulanonda, a former premier, of instigating the 2006 coup that ousted their patriarch, ex-prime minister Thaksin Shinawatra.

At least 10 branches of Bangkok Bank, where Prem is an hononary adviser, were set ablaze in the riots that erupted on Wednesday after the military swept into the red shirt protest encampment, forcing its leaders to surrender.

In another incident, 5,000 red shirt protesters in January demonstrated outside the home of another royal adviser, former army chief Surayud Chulanont, for his alleged illegal occupation of state forest land. He later gave the land to the state.

The government, has in turn, accused the red shirts of being republican, or worse yet, godless communists.

While few people voice publicly their worries about the monarchy, the markets have at times spoken louder than words.

Thailand's bourse .SETI tumbled and the baht THB= slid when the king was first taken to hospital in September.

The fact vague rumours could spark a sharp sell-off showed how worried Thais are about a change of monarch, and how badly Thailand's markets would be hit.

The current period of turmoil could only be worsened with such a change, as both sides in Thailand's political divide jockey for power.

In theory, Thailand's monarchy is above political divisions. Bhumibol is a constitutional monarch, with no formal political powers. Yet during six decades on the throne, the king expanded his influence on politics and explicitly intervened three times during periods of conflict between the military and elected officials.

Despite the king's silence in the current turmoil, the palace has been drawn into the fray, and the conflict has become partly about the future role of the monarchy.

Some worry that Thailand's divisions could end up politicising the monarchy in the future. Many Thais think that process has already begun.

They cite Queen Sirikit's attendance at the funeral of an anti-Thaksin protester killed in clashes with police in 2008. That fuelled suspicions of royal backing for a "yellow shirt" protest movement supporting the current government. (Editing by Ron Popeski )