Thais wear black, hold Buddhist ceremonies for deceased King Bhumibol

Bhumibol, the world's longest-reigning monarch, passed away at 88 on Thursday after a long battle with ill health.

Bangkok: Millions of Thais donned black Friday as the grieving nation prepared to hold traditional Buddhist ceremonies for revered King Bhumibol Adulyadej, whose death leaves the country facing an uncertain new era.

Bhumibol, the world's longest-reigning monarch, passed away at 88 on Thursday after a long battle with ill health, removing a stabilising father figure in a country where political tensions are still raw two years after a military coup.

Crown Prince Maha Vajiralongkorn, 64, is the king's named successor, but has made a surprise request to delay formally becoming the next king, according to the junta leader who appealed for citizens to accept the decision and "not cause chaos".

Officials prepared to move the monarch's body on Friday from the hospital where he died to the Grand Palace, a complex of glittering temples and pavilions in the heart of the capital.

Large crowds are expected to pour onto the streets for the procession from Siriraj Hospital where the king spent much of the last two years battling an array of ailments.

A statement from the palace said the Crown Prince would preside over a ceremony to bathe the king's body -- a traditional Buddhist funeral rite. His remains will then lie in state for weeks and months of palace rituals.

Many Thais on Friday opted to dress in black and white, both mourning colours in Thailand, as they went about their business.

"I am very sad, I was born under this king," Arunee Sahathongthai, 49, told AFP as she bought a pair of black trousers at a market in Bangkok, saying that Thais were "united in grief".

Some said they were nervous about a future without Bhumibol.

"I really loved him," Arnon Sangwiman, a 54-year-old electricity company employee, told AFP.

"Now I am afraid of what may happen, about the administration of the country, the type of regime in the long term."

Thais had expected Vajiralongkorn to be officially proclaimed king immediately after his Bhumibol's death was announced.

But Thailand's junta leader late Thursday announced that the prince had sought a delay to mourn his father's loss and better prepare for his new role.

The move could fuel concerns over the succession and test the ruling junta, which has vowed to ensure stability after more than a decade of political turbulence.

Most Thais have known no other monarch than Bhumibol and he was portrayed as a guiding light through decades of political turmoil and coups.

The Crown Prince spends much of his time overseas and is yet to attain his father's widespread popularity at home.

Analysts said the nation's elites likely want to stage a slow and careful transition.

The junta seized power in 2014 after a decade of strife between Thailand's two major political factions, exacerbated by the king's declining health as jostling elites competed for power.

The military has deep links with the palace and many inside the kingdom saw the putsch as a move to ensure generals could squelch any instability during a succession.

During Bhumibol's reign, Thailand transformed from an impoverished, rural nation into one of the region's most successful economies, avoiding the civil wars and communist takeovers of its neighbours.

He sometimes intervened to quell Thailand's frequent political violence but at other times stayed silent, approving most of the army's many coups during his reign.

Any criticism, republican sentiment, or speculation on succession is smothered by a draconian lese majeste law.

Tributes poured in from across the globe for the monarch.

President Barack Obama described Bhumibol as a "close friend" of the United States and a "tireless champion" of his country's development.