HUA HIN, Thailand - Thailand’s revered King Bhumibol Adulyadej made a rare public appearance Monday to mark the 64th anniversary of his coronation, as the political turmoil gripping his kingdom enters a critical phase.

Embattled prime minister Yingluck Shinawatra is facing two key legal challenges which could see her removed from office over the coming days, while opposition leader Abhisit Vejjajiva refused at the weekend to commit to elections mooted for July to end the political crisis.

King Bhumibol, the world’s longest-reigning monarch and a father figure for Thais, was crowned on May 5 1950, although he came to the throne in June 1946 following the death of his elder brother.

The 86-year-old monarch is seen as a moral authority in Thailand, which has been deeply divided along political lines since 2006.

King Bhumibol’s public speeches are closely scrutinised, especially in times of political crisis, but on this occasion he did not speak.

The streets of Hua Hin, near the coastal palace where the monarch has lived since leaving a Bangkok hospital last August, were a sea of yellow - his signature colour - as his vehicle passed, with thousands of people waving flags and shouting “long live the king”.

A short service was held in a room in the royal palace packed with Thailand’s political and military establishment, as well as senior members of the royal family, including the heir Crown Prince Maha Vajiralongkorn.

Monks led prayers as the king, who has suffered ill health for several years and uses a wheelchair, looked on.

Yingluck was also present. She has faced six months of protests demanding she steps down, which have left at least 25 people dead and hundreds more wounded, raising fears of wider violence between pro- and anti-government supporters as legal moves against her edge towards a conclusion.

She has been called to appear before the Constitutional Court on Tuesday against an allegation of abuse of power over the transfer of a top security official.

Critics accuse the court, whose nine members are appointed, of rushing through Yingluck’s case and allege previous rulings show that it is politically-biased against the Shinawatras.

In 2008, the court forced two Thaksin-linked prime ministers from office.

A member of Yingluck’s legal team said the premier had not confirmed if she will attend the hearing.

“It is an important case, we think the court should take time to carefully consider the case,” he told AFP, requesting anonymity.

Analysts expect Yingluck will be toppled by the court.

“The question is whether the court will extend the ouster to the rest of the members of the cabinet,” said Paul Chambers, director of research at the Institute of South East Asian Affairs at Chiang Mai University, adding to do so would plunge the country into “legal limbo”.

The premier could also be charged with neglect of duty by Thai anti-graft officials over a costly rice subsidy policy which could see her toppled and banned from politics.

It is not clear when either ruling will be made, but they are expected over the next 10 days.

Supporters of both sides have vowed major rallies in step with the verdicts, stoking concerns over clashes in a kingdom whose recent political history has been pock-marked by violence.

Thailand’s political schism roughly pits the Bangkok elite and middle class - as well as staunchly royalist southerners - against the Shinawatra’s electoral base in the northern portion of the country and many among the urban poor.

Abhisit, the leader of the opposition Democrat Party, last week called for Yingluck to resign to make way for an appointed interim premier who would oversee a referendum on reforms.

Elections could then be held, he said, but not on July 20 as already agreed by the ruling party and poll authorities.

Observers say his “roadmap” has failed to garner widespread support.

Thaksin, a tycoon-turned-politician, fled overseas in 2008 to avoid jail for a corruption conviction, but he is seen as pulling the strings behind his sister’s premiership and is accused by opponents of nepotism and rampant corruption.

But he is a hero to his mainly rural, poor supporters for recognising their burgeoning political and economic aspirations.

Shinawatra led- or allied-government have won every election since 2001.