Thai citizens gearing up to mourn the late King Bhumibol Adulyadej one last time, nearly a year after his death.  The cremation ceremony is slated to occur Thursday. 

More than 12 million people have visited the throne hall of the royal Dusit palace in the capital, Bangkok, where the late king's remains were housed, to pay their respects, according to a NPR report Wednesday. 

"Mourners have been gathering at the cremation site for several days now, some camped out in the heat and pouring rain in order to claim their spot for the royal cremation," said Michael Sullivan, a reporter for NPR. 

The ceremony is expected to bring as many as 250,000 attendees who come from across the country, the BBC reported Wednesday.

"I traveled here two days ago so that I could be the first to get a good spot," a 72-year-old woman from northern Thailand told Reuters on Tuesday.

Preparations for the late king's cremation were in the works for nearly a year, which included the construction of the cremation complex which neighbors the Grand Palace, according to the BBC. 

King Adulyadej died Oct. 13, 2016, at the age of 88, and the cremation ceremony will be the conclusion of a year-long mourning period. As a part of Buddhist tradition, mourners will be dressed in all black.

Public concern over the king's health was first ushered by his battle with pneumonia in 2009. Nearly 10 years before his death, King Adulyadej was rarely seen by the public eye due to continuing health issues. 

The late king was the longest reigning monarch — ruling for 70 years — and was beloved by many Thais, Sullivan added. 

Thailand's new monarch, King Maha Vajiralongkorn Bodindradebayavarangkun, became the new ruler in December 2016, however, the official coronation will not occur until after the cremation ceremony. 

"I would like to accept the invitation for the benefit of the Thai people," said King Bodindradebayavarangkun in a televised statement December 1. 

GettyImages-866082112 A woman holds an image of the late Thai King Bhumibol Adulyadej as mourners wait for his funeral to begin in Bangkok on October 25, 2017. Photo: Getty