Royal succession in Thailand will be seamless when it is eventually triggered, palace observers say, as the acutely taboo topic resurfaced on Wednesday following growing signs the health of the revered 88-year-old King Bhumibol Adulyadej is deteriorating.

Prime Minister Prayuth Chan-ocha abruptly cancelled a scheduled visit to the rural Chonburi province as the Thai stock market and the baht took a beating for the third straight day after an official statement over the weekend described King Bhumibol’s health as “unstable”.

The palace statement first released late Sunday said the world’s longest reigning living monarch was in a “generally unstable” condition after treatment to purify his blood and drain excess cerebrospinal fluid.

The statement said the king was put on a ventilator after his blood pressure dropped following the procedures. His doctors were monitoring him closely as “the overall symptoms of his sickness are still not stable,” it said.

In a fresh online statement on Wednesday afternoon, the government provided updates on how the public could “sign and write well-wishing messages” but did not give further updates on the monarch’s health.

Thai monarchy observers said the choice of words stood out from previous official updates on the ailing king’s health. The widely venerated monarch enthroned since 1946 has been out of the public eye in recent years due to a range of health issues including renal failure. The palace has released more frequent updates of his health this year.

Ailing Thai king's health 'not stable' after haemodialysis treatment, palace says

Commentary from within Thailand about the king’s health and succession plans is scarce because of the country’s tough royal defamation laws, which has seen increased usage under the current military government.

“This is an extraordinary statement from the Royal Household Bureau. Usually they try to say something positive, not this time,” said Kevin Hewison, a veteran Thai politics expert who is emeritus professor of Asian Studies at the University of North Carolina at Chapel Hill.

Serhat Unaldi, a Germany-based author of a book about the monarchy, said the phrase “not stable” is “indeed an unusual choice of words”.

“The king seems to be in a critical condition,” he said.

Patrick Jory, a Southeast Asian history expert at Australia’s University of Queensland, said the sharp drop in the Thai stock exchange on Monday following the announcement “is probably the clearest indication of public sentiment about this news”.

“If there is not another statement soon saying that the king is now ‘stable’, people will assume that his health remains ‘unstable’, which will likely cause further alarm,” said Jory, who specialises in the history of the Thai monarchy.

“Everyone is aware of the state of the king’s health, even though they cannot express it openly because of the sensitivity around the monarchy.”

King Bhumibol is the ninth king of the 234-year-old Chakri dynasty, and ascended the throne after his elder brother King Ananda Mahidol died in a mysterious shooting. The reigning monarch is widely respected for his role in restoring the prestige of the previously floundering institution and for acting as an unifying force in a country beset with deep-seated political divisions between city-dwelling elites and the rural poor.

The kingdom has seen 19 coups d’etats – including 12 successful ones – since absolute monarchy was abolished in 1932.

Foreign-based experts as well as Thailand-based political observers who chose to remain anonymous told This Week in Asia there is little doubt the current Crown Prince Vajiralongkorn, 64, will become king when his father dies.

“My view is that the prince will become king. I do not anticipate opposition. The junta has made it clear enough that they are behind the prince,” said Hewison, referring to the current administration led by former army general Prayuth Chan-ocha, who seized power in 2014.

Unaldi said he believed Vajiralongkorn’s position as the future king is “cast in stone”.

“There is no alternative to Vajiralongkorn. According to the Palace Law of Succession, he is the rightful heir to the throne,” said the author of Working Towards the Monarchy: The Politics of Space in Downtown Bangkok.

Jory said it will be difficult for many Thais to accept the death of the current monarch even as they prepare to witness the first coronation in many generations.

This is “because of the centrality of the monarchy and the long reign of the present king,” he said.

“It is likely that there will be a long period of mourning, perhaps up to a year or more,” he added.

Other experts said the death of King Bhumibol could compel the junta to push back a general election it said it would hold late next year.

Junta chief Prayuth said in August he would push through with the plan after voters backed a new military-crafted constitution in a referendum.

The country has not had polls since 2011, and has been bitterly divided since the 2006 coup against prime minister Thaksin Shinawatra, the billionaire telecom tycoon turned politician.

After the restoration of democracy, the military again intervened in 2014 to topple a government led by Thaksin’s sister Yingluck Shinawatra.

The Shinawatras are popular among Thailand’s north and northeast rural poor, but are opposed by the royalist elite.

Thai junta chief Prayuth abruptly cancels all official engagements to meet crown prince as king’s health fears grow

Hewison said in the event of the king’s death, the military will “postpone the promised election next year”.

According to Jory, the military rulers are likely to remain in power during the mourning period and until the royal succession is completed “in order to guarantee political stability”.

He added: “The test will come when Thailand returns to civilian rule and the ban on political activities is lifted”.

Jeffrey Halley, a Singapore-based senior market analyst with Oanda, said the Thai stock market and the baht would remain under pressure amid uncertainty about the king’s health.

“The King is universally revered by all sides and divides in Thailand and is regarded as a unifying influence and an arbiter in often messy politics behind the scenes,” Halley said.

“We expect the SET (Stock Exchange of Thailand) Index to underperform its regional peers until a clearer picture of the King’s health appears…the Thai baht will also continue to be under pressure,” he said.