Thailand's King Bhumibol marks 70 years on the throne

King Bhumibol inherited the throne in 1946 at the age of 18

Thailand has been marking 70 years since King Bhumibol Adulyadej, the world's longest-reigning living monarch, ascended to the throne.

The celebrations began with a religious ceremony in Bangkok, led by 770 Buddhist monks, an auspicious number.

The 88-year-old king is revered by Thais, for whom he has been a figure of stability through the country's decades of political upheaval.

But he is in poor health and has not been seen in public for months.

Profile: King Bhumibol Adulyadej

On Tuesday, he had heart surgery, with what the palace said were "satisfactory results".

The procedure, known as balloon surgery, was to widen his arteries after tests showed he had insufficient blood in the heart muscles, the statement said.

The 770 monks - an auspicious figure in Thailand - gathered at the Grand Palace in Bangkok

Thai Prime Minister Prayuth Chan-ocha was at the ceremony to give alms to the monks

The king has spent much of the past few years in hospital, and his health is closely watched by Thais.

"The relationship between Thais and the King is deep, more than one can actually begin to explain," Col Winthai Suvaree, a spokesman for the royalist junta, said to Reuters.

"He is a father to the land."

King Bhumibol was last seen was when the palace released a video of him being taken in his wheelchair to visit a shop inside a hospital in Bangkok

The 88-year-old king is seen as a unifying force in a country divided along political lines

Several hundred people gathered outside the palace on Thursday morning to wish the king well.

As expected, he did not make a public appearance.

"I want to make merit for the king to encourage him to have good health. That's how I can show loyalty to him even though he can't see it, that's fine," 68-year-old Bangkok resident Chonmanee Smativat told AFP.

"I want him to know that we all love him. He has worked hard for Thais. Since I was little I have seen how hard he works."

People across Thailand show their reverence for their king with multiple pictures of the monarch hung on their walls

Crowds gather whenever the king's convoy travels, and many sport yellow - symbolising royalty - on their birthdays

The king's popularity stems partly from his long reign and service to Thai people, but also because he is seen as an arbiter in politics.

Thailand has been wracked by political strife in recent years and is currently governed by a military-led government.

Strict lese majeste laws ban any criticism of the king or the royal family.