Bangkok, December 2:

Formal celebrations for Thai King Bhumibol Adulyadej’s 80th birthday kicked off today with a pomp-filled military parade, ahead of a week of elaborate festivities for the world’s longest-reigning monarch.

Bhumibol, whose birthday is on Wednesday, was expected to preside over the annual parade, in which the elite Royal Guards recite an oath of allegiance to the king, an accomplished musician who composed the music they march to.

Bhumibol’s health has recently been a matter of nationwide concern. He checked out of a hospital on November 7 after three weeks of treatment for a colon infection and what the palace described as inadequate blood flow to his brain. Bhumibol has suffered several ailments in recent years, including heart problems.

As part of the weeklong celebrations, Bhumibol is to address the nation on Tuesday night, as he does every year on the eve of his birthday.

Fireworks will light the skies on Wednesday night and many Thais will perform charitable acts to honor the king, such as donating blood. Across the Buddhist nation, people will also show respect for the monarch by performing merit-making ceremonies that typically involve freeing captive animals, including birds, turtles and fish.

The king was born on December 5, 1927, in Cambridge, Massachusetts, where his father, Prince Mahidol, was studying medicine.

He became the ninth king of Thailand’s Chakri dynasty on June 9, 1946. He succeeded his older brother Ananda, who died in an unexplained shooting.