MILLIONS of Thais were disappointed last night when King Bhumibol Aduladej failed to read an address to the nation on the eve of his birthday.

Instead, Crown Prince Maha Vajiralongkorn read the speech marking the king's 81st birthday.

It was the first time in memory the king had not given his own speech and came as Thais looked to him for guidance through the country's political crisis.

The crown prince said on radio that the king was "mildly sick." Prince Maha Chakri Sirindhorn, the king's daughter, said in the same broadcast that King Bhumibol "has a blockage in his throat and has poor appetite".

Although the king has no direct role in politics, his influence over 65 million Thais became paramount as his stature and popularity grew over the course of his six-decade reign.

He has issued guidance in the past to end political upheaval.

The announcement came as ruling MPs met to discuss who they would nominate when they reconvene Parliament, probably on Monday, to appoint a new prime minister to replace Somchai Wongsawat.

Mr Somchai was banned by court order from politics on Tuesday and his party dismissed for electoral fraud.

Anti-Government protesters in the People's Alliance for Democracy who occupied Bangkok's airports for eight days are threatening more crippling protests if MPs elect a prime minister they regard as a proxy for the ousted and exiled former prime minister Thaksin Shinawatra.

They accuse Mr Thaksin of wanting to create a republic, a threat to the monarchy.

The caretaker Prime Minister, Chaowarat Chandeerakul, said yesterday that despite the loss of Mr Somchai and 59 other executives from three parties for electoral fraud, the ruling coalition was still strong enough to form a pro-Thaksin government.

Bangkok's Subarnabhumi international airport will officially reopen today. Qantas plans to resume flights to Bangkok tomorrow.