It is his 86th birthday on Thursday, an occasion Thais will mark with a holiday, and it would be seen as disrespectful to the world's longest ruling monarch to make trouble.

At the height of fighting on Monday, a tear gas canister was mistakenly lobbed in the grounds of Suan Kularb palace in Bangkok's historic quarter, the home of Princess Somsavali Kitiyakara. A royal member at the palace summoned Bangkok police chief Kamronwit Thoopkrachang and told him Thais must not fight Thais. General Kamronwit said later he replied by stressing the importance of showing loyalty to the royal family.

Within 24 hours, police called a halt to the battle outside Government House and the city's police headquarters, removed barbed wire and concrete barriers and allowed protesters to enter the grounds, where they celebrated a partial victory in surreal scenes that could only be witnessed in a country promoted as the "The Land of Smiles".

However, as a clean-up of Bangkok's streets began ahead of birthday parades, reports emerged that it was not police who manoeuvred the protagonists into taking time-out to celebrate the birthday but Thailand's powerful military, whose generals have been insisting they have remained neutral in the conflict that threatens the government of Prime Minister Yingluck Shinawatra.

Well-informed Thai journalists reported the military acted as the mediator in secret negotiations for a birthday truce between protest leaders and the government. It has also emerged the military has been playing a greater role behind the scenes as Ms Yingluck's government faced its biggest challenge since winning democratic elections in 2011.

Last Sunday night, Army Chief Prayuth Chan-ocha hosted a meeting at the King's bodyguard unit, the 1st Infantry Regiment, where Ms Yingluck was confronted by firebrand protest leader Suthep Thaugsuban, a man who was wanted at the time on charges of inciting violence, later upped to treason and a possible death sentence. Ms Yingluck asked Mr Suthep, an old school Thai politician, what he really wanted, adding she came to power through democratic elections.

"I run the country on my own without listening to my brother," she said, referring to Thaksin Shinawatra, the billionaire fugitive living in self-imposed exile in Dubai.

Instead of being arrested, Mr Suthep demanded the Prime Minister dismantle her government and hand over power to a vaguely defined people's assembly.The tense meeting broke up without resolution after 30 minutes, Thailand's Nation newspaper reported.

Academics have questioned the role of the military in negotiating the meeting as the country's seats of power were being attacked and occupied.

"The military has a role to maintain stability. Why didn't the commander tell Suthep to stop his movement," said independent academic Assadang Panikabutr.

Another academic, Trakul Meechai, said the military "should come out and make its role clear but not stage a coup".

General Prayuth maintains the military is remaining neutral during the crisis, but army officers were seen on the streets urging police not to use violence against the protesters.

The military has staged 18 coups or attempted coups since the 1930s, the last in 2006 to oust Thaksin Shinawatra, a popular figure in rural Thailand who is despised by many of Bangkok's elite and middle class. Analysts say another takeover is possible if the crisis worsens.

"The military might wait for a very opportune time to make a move to intervene in the affairs of the government, which might possibly be followed by a coup if they assume the situation has turned violent or the government could no longer control it," said Pavin Chachavalpongpun of Kyoto University's Centre for Southeast Asian Studies.

The Thai supreme military commander, Thanasak Patimapagorn, has called a meeting of all armed forces commanders after King Bhumibol's birthday, signalling that the military sees itself as continuing to play a role in a crisis that Mr Suthep insists will continue.

"You can rest assured that this is a victory that is only partial ... because the tyrannical Thaksin government endures," Mr Suthep said, referring to the celebratory scenes. "We must continue fighting."