Thailand's revered King Bhumibol Adulyadej has a throat infection and is on a drip, the crown princess said on Thursday after he failed to make his traditional birthday eve address amid a crippling political crisis.
Many Thais had been looking to the king, who turns 81 on Friday, to issue a call for unity after the deepening crisis saw Bangkok's main airport shut for a week by anti-government protesters.
"Yesterday when I saw him he looked OK. He could eat what we served him, but today he had a throat infection so he could barely eat," Crown Princess Maha Chakri Sirindhorn said in remarks broadcast from the ceremonial hall via national radio.
"Therefore, the doctors prescribed him medicine and put him on a saline drip," she said.
Regarded as semi-divine by many Thais, he has intervened decisively in politics three times during his six decades on the throne, favouring both democratic and military administrations.
His remarks in the last three years have been nuanced and focused on the need for national unity, although his calls for clean government were widely read as a swipe at Thaksin Shinawatra, the populist prime minister ousted in a 2006 coup.
Crown Prince Vajiralongkorn, who deputised for his father, said the king was "slightly ill".
The monarch has been thrust into the centre of the political fray by the anti-government People's Alliance for Democracy's (PAD) persistent invocation of his name.
Bringing hope to 230,000 stranded foreign tourists, Airports of Thailand said the $4 billion Suvarnabhumi airport, one of Asia's largest, would resume "full service" at 0400 GMT on Friday after a week-long shutdown by PAD protesters.
Thai Airways said it operated 12 flights out of the 125,000 passenger-a-day hub on Thursday, but sources said other carriers were being rail-roaded into getting back in the air and were worried about the effect of short-cuts on safety and security procedures.