Hundreds of thousands of Thais have lined the streets of Bangkok to pay their last respects to the late king.
A symbolic funeral urn was taken by chariot to the cremation site, in a procession marked by drums, flute music and an artillery salute, as the main part of a five-day funeral ceremony.
Many buildings are draped in yellow marigolds, while crowds of mourners are dressed in black as a mark of respect.
The revered king Bhumibol Adulyadej died in October 2016 aged 88.
The funeral officially started on Wednesday with a merit-making ceremony, a Buddhist rite, in the Grand Palace.
On Thursday, a series of Buddhist rites began in the royal palace ahead of the procession.
The late king will be cremated later in a royal pyre to be lit by his son, King Maha Vajiralongkorn.
The chariot carrying the urn in the second part of the funeral procession has been used since the late 18th Century. Weighing just under 14 tonnes, it was pulled by more than 200 soldiers.
The urn was then carried for several rounds around the cremation site, for the last leg of the procession.
The elaborate ceremony is estimated to have drawn as many as 250,000 people from across Thailand.
Many of the mourners arrived at the capital days ago, and waited in the streets overnight for the procession, clutching portraits of the late king.
Thursday has been declared a public holiday, with many businesses shut all day or closing at midday.
Members of royal families and dignitaries from more than 40 countries are attending the ceremonies.
King Vajiralongkorn will light the funeral pyre at 22:00 local time (15:00 GMT) and his father’s ashes will be collected and transported back to the palace on Friday.
Two more days of ceremonies will follow.
The late king was seen as a stabilising figure in a country hit by cycles of political turmoil and multiple coups.
Since his death on 13 October 2016, Thailand has observed a year of official mourning, with many people wearing black.
Preparations for this week’s events took almost a year and have included setting up the large cremation complex near the palace.
The funeral site features sculptures of mythical creatures and auspicious animals such as lions and elephants.
According to Buddhist tradition, the funeral rituals are modelled after the universe and the cremation pyre represents a sacred mountain.
The funeral ceremonies come with strict guidelines for those attending. Thailand’s lese-majeste law, which forbids any insult to the monarchy, is among the harshest in the world.
Roads across Bangkok’s historic centre are shut for the day and while tourists are not expected to wear black like most Thais, they have been asked to dress and behave respectfully.