Bangkok, Thailand ? Royalty from around the world Monday watched a spectacular procession of gilded boats honoring Thailand’s king, the world’s longest-reigning monarch celebrating his 60th anniversary on the throne.

More than 2,000 oarsmen rowed ceremonial boats on Bangkok’s Chao Phraya river in the highlight of a five-day celebration for King Bhumibol Adulyadej.

Representatives of 25 royal houses from Europe, Africa, the Middle East and Asia watched from a riverside pavilion as the vessels – bows adorned with figures of serpents, swans and a seven-headed dragon – glided by to a haunting call-and-response song honoring the king.

Bhumibol, a constitutional monarch with limited powers, has used his high prestige to pressure opposing parties to compromise during political crises. He is credited with helping keep Thailand more stable than many of its Southeast Asian neighbors.

Many Thais are counting on him to pull the country through its current political crisis, which has left it with no functioning legislature and only a caretaker government after a divisive, inconclusive election.

Bhumibol was born Dec. 5, 1927, in Cambridge, Mass. He became the ninth king of Thailand’s Chakri dynasty on June 9, 1946, succeeding his older brother, Ananda, killed by an unexplained shooting.