Profile: King Bhumibol Adulyadej
King Bhumibol Adulyadej is the world's longest reigning monarch.
King Bhumibol is the world's longest-reigning monarch
Revered by an adoring public, the 81-year-old king is seen as a stabilising influence in a country which, during his reign, has seen numerous military coups, 17 constitutions and even more prime ministers.
Thailand's economy is now more than 40 times the size it was when he came to power 63 years ago.
Seen as a benign father figure who remains above politics, King Bhumibol has nevertheless been credited with intervening at a few moments of acute political tension to find a non-violent resolution.
His usually opaque public utterances are minutely dissected for advice to the nation.
Though he is a constitutional monarch with limited powers, most Thais regard him as semi-divine.
Hundreds of thousands gathered to hear him speak in June 2006 when he celebrated 60 years on the throne, and any sign he has medical problems is seen as a matter of national concern.
King Bhumibol Adulyadej acceded to the throne on 9 June 1946 after his brother, King Ananda Mahidol, died in a still unexplained shooting accident at the Royal Palace in Bangkok.
He was born in Cambridge, Massachusetts, where his father was studying, and he was later educated in Switzerland. He returned there to finish his studies before returning to Thailand where he was crowned in May 1950.
King Bhumibol met the UK's Queen Elizabeth II in 1996
The status of the monarchy had been in decline since the abolition of absolute monarchy in 1932, and then the abdication of King Prajadhipok, King Bhumibol's uncle, in 1935.
In his early years King Bhumibol was overshadowed by a series of powerful military leaders.
But he rebuilt the monarchy's profile through a series of tours in the provinces, and through numerous royal projects that established his lifelong concern with agricultural development.
In 2006, then UN Secretary General Kofi Annan presented him with the United Nations' first Human Development Lifetime Achievement Award.
The current public reverence for King Bhumibol appears genuine, but it has also been carefully nurtured by a formidable palace public relations machine, and by harsh "lese-majeste" laws that punish any criticism of the monarchy with up to 15 years in prison.
King Bhumibol's first public intervention in Thailand's chaotic politics occurred in 1973, when pro-democracy demonstrators were fired on by soldiers and were allowed to shelter in the palace, a move which led to the collapse of the administration of the then prime minister, General Thanom Kittikachorn.
But he failed to prevent the lynching of left-wing students by paramilitary vigilantes three years later, at a time when the monarchy feared the growth of communist sympathies after the end of the Vietnam War.
Celebrations for the 60th year of the king's rule were lavish
In 1981, King Bhumibol stood up to a group of army officers who had staged a coup against the prime minister, and the king's personal friend, General Prem Tinsulanond. Units loyal to the king then retook Bangkok.
In 1992 he again intervened when dozens of demonstrators were shot after protesting against an attempt by a former coup leader, General Suchinda Kraprayoon, to become prime minister.
The king insisted on a new election and democracy was subsequently restored.
During the crisis that erupted over the leadership of Prime Minister Thaksin Shinawatra in 2006, the king was frequently asked to intervene but insisted this would be inappropriate.
However his influence was still viewed as pivotal when the election Mr Thaksin had won that April was quickly annulled by the courts. His precise role in the coup that deposed Mr Thaksin is unknown.
Three years on, the king's name and image are invoked by factions both for and against Mr Thaksin, who are still jostling for power.
The entire country joined lavish celebrations to mark King Bhumibol's 80th birthday in 2008, and in the months leading up to it millions of Thais took to wearing his colour, yellow, to bring him good luck.
In his younger days, King Bhumibol enjoyed a wide variety of pursuits, including photography, playing and composing songs for the saxophone, painting and writing.
He even received a patent for his development of an artificial rain-making technique.