(Corrects Prayuth's 2006 rank to deputy regional commander in par 18)
By Amy Sawitta Lefevre
BANGKOK, Jan 10 (Reuters) - Standing inside one of Bangkok's many military bases is a giant poster of Thai army chief Prayuth Chan-ocha in full dress uniform, along with a list of attributes. "Intelligent," reads the poster. "Knowledgeable. Modern. Visionary."
As Bangkok braces for a "shut down" by anti-government protesters on Monday, and rumours multiply that yet another military coup is imminent, another adjective for General Prayuth springs to mind: opaque.
Paralysing Bangkok is the latest bid in a two-month attempt by protesters to topple Prime Minister Yingluck Shinawatra, whose brother, Thaksin, was overthrown in the last military coup in 2006.
Yingluck called a snap election for Feb. 2, but this failed to mollify protesters, who want her government to resign in favour of an unelected people's council to oversee political reform.
Many Thais believe the military will soon step in again to break the political deadlock, especially if next week's citywide protests turn violent.
But Prayuth, 59, has remained noncommittal, brushing aside rumours of a military coup while deftly side-stepping an outright denial.
It wasn't always so. Famous for irascible exchanges with the media, Prayuth once suggested coups were obsolete and slammed rumour-mongers for damaging the country.
As Thailand's latest round of protests gathered pace, however, his public statements have fuelled rather than scotched the rumours.
"I cannot confirm whether there will or will not be a coup," he said on Jan. 7.
Two weeks earlier, Prayuth likened the unrest between pro- and anti-government protesters to an intersection where he had the power to "turn the lights red" to stop traffic from left and right colliding.
"The odds of an all-out military coup remain lower for now but will increase as instability drags on," said Christian Lewis, a Southeast Asia specialist at political risk consultants Eurasia Group. "Prayuth and the military will most likely intervene only if the police lose control of an eroding security situation."
Thousands of protesters have taken to Bangkok's streets since November, accusing the Shinawatra family of corruption and nepotism.
The protests, which have drawn 200,000 people at their peak, have been mostly peaceful.
Four people, including two police officers, died of gunshot wounds and scores were injured after protesters clashed with police outside a stadium on Dec. 26 while candidates registered for the election.
In broad terms, the current crisis pits the Thai elite, including military generals and royalists, and the educated middle-classes against supporters of twice-elected former prime minister Thaksin, who now lives in self-imposed exile to avoid jail for a graft conviction he says was politically motivated.
But with Yingluck clinging onto power and protesters refusing to back down, analysts say protest leader Suthep Thaugsuban, a former deputy prime minister, can only win with Prayuth's backing.
That has sparked fears that protagonists might instigate an attack on protesters during next week's rallies in hopes of provoking army intervention.
But senior officers told Reuters the military is reluctant to see a repeat of the September 2006 coup, which Prayuth helped execute as a deputy regional commander and plunged the country into years of turmoil.
"Prayuth is aware that dealing with the problem by staging a coup is not constructive and, after a while, the same problems will come back again," said army spokesman Colonel Werachon Sukhondhadhpatipak.
Born in northeast Thailand, now a stronghold for Thaksin supporters, Prayuth has a reputation for "hard-headed decisiveness", wrote Anthony Davis, a Thailand-based analyst at security consulting firm IHS-Jane's, after Prayuth was appointed in October 2010.
"An officer of polished social skills, he has become a regular visitor to the palace, suggesting that in royal circles he is seen as a vital figure to ensure the future stability of both the nation and the monarchy," said Davis.
Prayuth also established a cordial relationship with Yingluck after her election the following year. He has repeatedly said he wants the military to remain politically neutral.
Yet Prayuth, who is a few months shy of mandatory retirement, commands a highly politicised army. It has played a pivotal role in a country that has seen 18 successful or attempted coups in the past 81 years.
"Prayuth was involved in a coup once before and knows that after a coup come many obstacles," said Boonyakiat Karavekphan, a political analyst at Ramkamhaeng University in Bangkok.
"He has shown no political ambitions but even if he did, staging a coup today is much more difficult than in 2006. Thailand is a different country and he risks upsetting the politically awakened masses," he said, referring to Thaksin's supporters who would be outraged if his sister's government was overthrown.
Prayuth faces another dilemma from some rank-and-file soldiers in green uniforms dubbed "watermelons" - green on the outside with red, pro-Thaksin, sympathies on the inside.
Fissures within the army were evident during a bloody April and May 2010 crackdown on pro-Thaksin red shirts in Bangkok who were demanding fresh elections and the resignation of pro-establishment Prime Minister Abhisit Vejjajiva.
Some soldiers openly sympathised with red-shirted protesters, tipping off the group's leaders ahead of a planned army operation, unnerving the top brass and sapping troop morale. Ensuing clashes between soldiers and anti-government protesters killed 91 people. More than 2,000 were wounded.
"Last time the objective was to protect the Abhisit government which many soldiers disliked. But this time any decision by the generals will be made carefully and to protect national interests and all sides," said army spokesman Werachon.
"Of course, there are some 'watermelon' soldiers but they know that, as an army, we have to present a united front."
Compounding the situation is the complex web of loyalties within the army establishment.
Prayuth belongs to a powerful clique that includes retired former defence minister General Prawit Wongsuwan and former army chief General Anupong Paochinda, who both despise Thaksin.
A Dec. 13 Reuters report revealed both men secretly back protest leader Suthep and his ambitions to eradicate Thaksin's influence from Thailand. Prayuth is pulled between his loyalty to Anupong and Prawit, and his desire to restore the army's image after the 2010 clashes.
When Thailand was hit by its worst floods in decades in 2011 he went on a media blitz to promote the army by sending soldiers to help civilians. (Editing by Andrew R.C. Marshall and Robert Birsel)