The king, who is the world’s longest-serving monarch, has spent most of the last few months in hospital as fears over his health mount in a nation where he is seen as unifying, father-figure throughout a turbulent six-decade rule.
“A team of royal physicians examined the king on Thursday evening… and agreed that he is not ready to grant a royal audience therefore they have recommended he cancels royal activities,” the Royal Household Bureau said in a statement early Friday.
In October the king underwent an operation to remove his gall bladder after tests revealed it was swollen.
He was last seen in public in early November.
The king’s birthday — also known as “Father’s Day” in Thailand — is a public holiday and Thais traditionally wear the royal yellow as a sign of devotion to the monarch, while roads are lined with royal flags.
Elaborate celebrations were expected at the royal palace in Bangkok, where the king traditionally makes an appearance and gives a brief statement to his subjects.
He last failed to make an appearance in 2008 for his 81st birthday celebrations following ill health.
Crown Prince Maha Vajiralongkorn was already expected to carry out some official ceremonies to mark his father’s birthday.
Most Thais have only known King Bhumibol on the throne and anxiety over the future once his six-decade reign ends is seen as an aggravating factor in Thailand’s bitter political divide.
His period as a constitutional monarch has been pock-marked by nearly 20 attempted or successful coups, the last in May which saw the army topple the elected government.
Thailand remains under martial law, a condition the arch-royalist army says is necessary to keep the peace as it vows to expunge the kingdom of corruption and reboot Thai democracy.
Critics of the military say it has used its status as the defender of the monarchy as a pretext to grab power from the elected government aligned with Thaksin Shinawatra — the billionaire self-exiled former premier whose emergence as an electoral force in 2001 shook up Thai politics. (AFP)