The monks wanted to wish the king a speedy recovery

The monks - led by the ageing Thai Buddhist leader, the Supreme Patriarch - crowded inside the ornate Temple of the Emerald Buddha for the ceremony.

Their chants, in the two ancient languages of Pali and Sanskrit, were specially focused on the much-loved king.

King Bhumibol, the world's longest-reigning monarch, underwent his operation on Tuesday.

On Thursday, the Bureau of the Royal Household said he was already back on his feet and recovering well.

The 75-year-old monarch was diagnosed with a hernia problem on his right side in November, which was found to have worsened by January.

King Bhumibol has had a series of health scares in recent years.

Last June he had a successful operation to treat a hernia on his left side, and in February 2002 he was admitted to hospital for prostate surgery.

King Bhumibol has been on the throne since 1946. He is regarded highly by his people, and some even see him as a god-like figure.

He has been a powerful force for unity, despite the political upheavals seen in Thailand's recent history.

He has seen more than 20 prime ministers, 16 constitutions and 17 coups since he became king at the age of 18.