Birds, dogs, cats, and snakes were burnt to death in their cages in the pet zone, which also included rats, pythons, and geckos.
The blaze was started by an electrical short circuit, authorities said, adding that no human casualties or injuries have been reported.
The incident prompted renewed calls for authorities to shut the pet zone, which has long been criticized for the animals’ poor living conditions and has reportedly led to high rates of disease and death.
With tens of thousands of shops crowding narrow lanes, Chatuchak is one of Southeast Asia’s biggest markets.
It’s also the largest and best-known of Thailand’s weekend markets. It claims to draw nearly 200,000 tourists every Saturday and Sunday.
But the portion of the market selling pets is open through the week. This accounts for about four of the 27 sections in Chatuchak market and is arguably its most controversial trade.
This zone of the market is subjected to regular inspections.
“When I got here, everything was gone, all burned down,” says Amporn Wannasut, a shop owner who rushed to the market after being alerted to the fire.
“I couldn’t do anything because it was dark inside as well. I couldn’t help them at all. They were all gone.”
The 42-year-old sold turtles, pythons, and king snakes, among other reptiles, as pets.
“I don’t even know what to do next. I think we have to start all over again but I don’t know how,” she adds. “I froze some of the dead snakes so that we can calculate how much [money] we lost.”
The fire damaged most of the 118 shops in the pet zone, which covers about 1,400 sq meters (15,000 sq feet), according to a preliminary inspection.
When the BBC arrived at the market on Tuesday afternoon, shop owners were standing in line to register their requests for compensation. Some of them looked distraught and several were crying.
There were also people taking selfies in front of the destroyed shops, even as police officers warned them not to go near the affected structures, which could collapse.
Recounting her narrow escape, a shop owner called Meecha told online news outlet Thaiger that she was awakened by the animals’ cries in the loft above her shop.
“Suddenly, thick smoke filled the air, making it impossible to breathe,” said Meecha, who climbed through a window to safety.
Some shop owners do live in the market, but it’s unclear how many were there when the fire broke out.
According to the Chatuchak District Office, the blaze started around 04:10 local time on Tuesday (21:10 GMT on Monday) and was extinguished 30 minutes later.
Pictures online showed extensive sections engulfed in flames and cages charred. Some appear to have been burned out of shape.
The People for the Ethical Treatment of Animals (Peta) group said the fire “underscores the urgent need for action.”
“Animals are not ours to use for our entertainment… Peta urges the Thai government to ensure that this facility, where captive animals suffer, never reopens,” said the group’s senior vice-president Jason Baker.
The Wildlife Friends Foundation in Thailand described Chatuchak market as a “shame on Bangkok”.
“Many of these poor animals are smuggled into the country, often illegally. It is immoral, cruel, a health and safety hazard, and completely unnecessary,” the foundation’s director Edwin Wiek said.
“The Bangkok Metropolitan Administration needs to act and stop this senseless cruelty to animals,” he said.