Bangkok - Thai King Bhumibol Adulyadej on Thursday did not show up to deliver his annual birthday-eve speech at Chitralada Palace for the first time in decades. He will turn 81 on Friday.

His daughter, Princes Maha Chakkri Sirinthorn, said the king was having trouble swallowing his food and suffering from congestion.

"His condition is not serious. He doesn't have a fever," Sirinthorn told a gathering of more than 22,000 government officials, civil servants and ordinary people who had gathered at the Dusit Hall in the palace to listen the king's annual birthday-eve speech, deemed one of the most important political weathervanes of the year.

It was the first time in decades that King Bhumibol, who has been on the throne for the past 62 years, had failed to deliver the annual address to the nation.

The unprecendented failure to make his birthday speech comes at a time of great political confusion in Thailand.

Last week anti-government protestors seized Bangkok's two airports in their efforts to topple the government, crippling the economy in the process by cutting off air traffic for the country's exports and tourism sector, both major foreign exchange earners.

The siege was finally lifted Tuesday after the Thailand Constitution Court dissolved the ruling People Power Party and banned its top executives from politics for committing election fraud in the December 23, 2007, polls.

The verdict automatically forced the former Prime Minister Somchai Wongsawat to step down, as he was a senior executive in the People Power Party.

The PAD, which has called itself a pro-monarchy movement, claimed the court verdict as a victory and lifted their siege at the airports on Tuesday, departing the facilities on Wednesday.

The PAD, a loose coalition of groups united only in their desire to keep former prime minister Thaksin Shinawatra from returning to power, is known to have the backing of Thailand's political elite.

The military and police have largely refrained from crackling down on the movement, demonstrating the powerlessness of the government.

Under Thailand's constitutional monarchy, the king is head of state, but has few political powers.

But King Bhumibol has over the years amassed immense moral power by staying above politics and intervening only at times of political crisis.

In 2006, King Bhumibol marked his 60th year on the Thai throne, and last year celebrated his 80th birthday, a cause for nationwide celebrations.

Last month the king presided over the royal funeral rites for his elder sister, Princess Galyani Vadhana, who died in January this year from cancer. She was 84 when she died.

Bhumibol is the world's longest reigning monarch and is much revered among the vast majority of Thais for his lifelong dedication to development projects and improving the livelihoods of the poor. (dpa)