The fire broke out at midnight local time in a restaurant in the Chatuchak district in the central part of the Thai capital. According to Thai PBS television channel, at least 30 people have died.
The rescue services have so far identified 17 women and eight men, the television channel reports.
Images shared online by the fire department show flames shooting out of the pub's main entrance as people try to escape and thick, black smoke rising into the sky.
"Most of the victims ran to the back, to the toilets where there was no exit. It may have been due to panic because there was smoke and fire in the room," Anutin Charnvirakul told reporters, according to AFP.
It took about half an hour for firefighters to bring the fire under control, according to authorities. Pictures from the restaurant show charred tables and chairs and the destroyed interior.
What caused the fire is unclear. The prime minister said on TV that musicians at the pub described "smoke from a switch near the stage." The power then went out, followed by an explosion.
The Ministry of Foreign Affairs is currently not aware of any Swedes among the injured or dead.
Thailand has experienced similar tragedies before. In 2022, 14 people died in a fire at a bar in the eastern part of the country.
