Compounding the atmosphere of uncertainty, on Friday Thailand's caretaker government said it had cancelled a planned special session of parliament scheduled for Monday, which would have elected a new prime minister.
"There were great expectations that awaited this speech and it had been a collective hope that he would be the saviour of the day"
"I am worried. I think all Thais are worried. Thailand needs him," Rojana Duangkaew, a 28-year-old pharmacist, told the Associated Press after hearing of the king's illness.
"He is the only one who can make people on both sides realise they are ruining the country. He is the only one who can unify Thailand."
Thailand has been gripped by months of political tensions, with mass street demonstrations by anti-government protesters descending into sporadic outbreaks of violence.
In the past two weeks, the country has seen a week-long siege of Bangkok's two main airports by anti-government protesters, and the ouster of its government.
The protesters ended their airport blockade on Tuesday after Thailand's constitutional court ordered the prime minister to stand down, barring him and several members of his coalition from politics.
With the crisis easing but still unresolved, there had been hopes that the king's speech would provide some guidance.
"There were great expectations that awaited this speech and it had been a collective hope that he would be the saviour of the day," Thitinan Pongsidhirak, a political scientist at Bangkok's Chulalongkorn University, told the Associated Press.
|Anti-government protesters have said they are acting in the king's name [EPA]
Few details have been released on the king's condition, but Princess Sirindhorn, the monarch's sister, said that the king was weak and suffering from bronchitis and inflammation of the oesophagus, but that his condition was "not serious".
Seen as semi-divine by many of Thailand's 65 million people, the king has intervened in politics three times during his 62-year reign, variously favouring elected and military administrations.
The People's Alliance for Democracy (PAD), who have spearheaded the anti-government protests, have made their allegiance to the king one of their central messages, and have reiterated that the aim of their struggle is upholding the values he is said to hold.
Many PAD protesters have donned yellow clothing during their demonstrations - a colour traditionally associated with the monarchy.
The political crisis started with mass protests in late 2005 against the government of Thaksin Shinawatra, the then prime minister.
The protests eventually culminated in a bloodless military coup in September 2006 which was widely believed to have been backed by the palace.
Thaksin's supporters won elections held in December 2007, but the PAD rejected the outcome, saying the new government was a proxy for Thaksin, and began another round of demonstrations which culminated with the seizure of Bangkok's airports.
PAD 'to be sued'
With the airport protests now ended, officials are trying to return the country's transport network to normal and said they expected "full service" to resume on Friday at the main Suvarnabhumi international airport.
The crisis however has cost Thailand's tourist industry millions of dollars in lost earnings and badly tarnished the country's reputation.
The chairman of Thai Airways, the national carrier, has said the company is considering suing the PAD for financial losses caused by the siege.
Surachai Tansitpong said the week-long blockade, which forced the cancellation of hundreds of flights and stranded more than 300,000 travellers, had cost the airline about $560m.
"The board has agreed that we have suffered losses as a public company, so those people who caused this must be held responsible," he said.
Tourism rescue plan
The Thai government, meanwhile, is considering a $625m rescue package for the tourism industry, including a campaign to rebuild the country's image abroad, an official said on Thursday.
The government has also set aside a budget of $68m to help many of the thousands of travellers stranded by the closure of the airports.
"The cabinet has already approved in principle a healing operation to help stranded passengers return home," Sasithara Pichaichannarong, the tourism and sport ministry permanent secretary, told the AFP news agency.
Sasithara also said that the ministry was discussing a plan to give $570m in loans for Thai tourism and tourism-related businesses to help revitalise the industry.