Brahmin priests, drummers and soldiers in ceremonial uniforms led a solemn but colour-splashed procession through Bangkok's historic heart on Thursday as Thailand bade farewell to King Bhumibol Adulyadej whose death left the nation without its chief unifying figure.

Some 300,000 black-clad mourners packed the streets, some weeping and prostrating themselves on the ground as a golden chariot carrying the royal urn snaked through the city in the blazing heat.

Brahmin priests untied their ponytails in an outpouring of grief before the royal urn was moved to a gun carriage to circle the funeral pyre three times ahead of the evening cremation.

The lavish event gave the public a chance to say a final goodbye to the monarch known as “father of the nation” who was crowned in 1950 and towered over decades of Thai history.