Flames crackle through piles of hundreds of human skulls and thick gray smoke pours into the Thai sky in a moment as spiritually significant as it is gruesome.
The Lang Pacha ceremony is observed by Thais of Chinese descent to give a dignified funeral to the unclaimed dead.
In Thailand, hospitals hand over unidentified bodies and those with no one to give them appropriate last rites to local foundations.
These then bury the corpses in graveyards, sometimes for several years, before a weekslong ritual when they are exhumed, cleaned and all cremated together.
In Buddhist belief, the spirits of the uncremated remain trapped between worlds and cannot be reincarnated until monks perform the proper rites.
"Spirits without cremation still roam," said Pisit Pongsirisupakul, vice president of the Dhamma of Buddha Nakhon Ratchasima Foundation, which organized the event.
"They suffer and they can't be reborn. We help them move on, and that's why this is an act of merit," he told Agence France-Presse (AFP).
Buddhists believe death marks the beginning of a new life, and making merit ensures a better rebirth.
"It's not scary," said Pisit. "When people die, we all look the same – like skeletons."
The ritual begins with volunteers digging up the graves – the event's name translates as "cleaning the jungle" – before brushing dirt and flesh from the remains and washing them in holy water boiled with tea leaves.
One man scrubbed out an empty eyesocket firmly with a toothbrush.
The scene is incongruously cheerful: wearing blue surgical gloves, Pimjai Sornrach grinned broadly as she held a skull, declaring "it's so good, it's so good," while her smiling friend held up a femur for the camera.
"I just want to be there whenever there's an event like this," said Pimjai, a 54-year-old shopkeeper.
She started volunteering at 17 after seeing two people killed in a hit-and-run, and says the ritual is about helping others as well as earning merit.
"My heart tells me to go."
Accumulated over the course of a decade, some of the 600 corpses were only recently deceased and the smell of death hung over the foundation complex in Nakhon Ratchasima province, north of Bangkok.
Some will have been Alzheimer's patients who wandered from their homes, never to be found by their families, others include road accident victims or undocumented laborers from Myanmar.
Laid out to dry, the remains are combined and divided up by bone type and laid out on mats or piled in buckets – hundreds of skulls, leg bones and others.
It is a family occasion – two young girls sat alongside rows of skulls, each holding an anonymous head in their lap.
In the days running up to the ceremony's climax, volunteers press gold leaf onto the bones, and reconstruct faces on a few.
Each set of bones is loaded by turn into two separate crematorium towers – one for the men, one for the women – with the skulls on top completing the stacks.
Monks chant and pray before the flames are lit. Later, the ashes from each tower will be interred in a graveyard.
Thitiwat Pornpiratsakul, 63, began volunteering after he, his wife and two sons survived a bus crash 20 years ago.
"Our bus flipped over, and no one came to help us," he recalled. "My wife and children were with me. We felt helpless."
Since recovering, he has taken part in the ritual every year.
"My family and I have stayed healthy, and I believe it's because we help in this ceremony," he said.
Organizers say the event not only honors the dead, but also highlights a need for legal reform.
Pisit has long campaigned for government support to expand DNA testing and connect the civil registration system to police forensics to help identify the unclaimed.
"We need a centralized database where families can search by ID and find their loved ones," he said.
