The fire broke out just after midnight local time at 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.
It took firefighters about half an hour to bring the fire under control, authorities said. Pictures from the restaurant show charred tables and chairs and the destroyed interior.
What caused the fire is unclear, but the incident is being investigated.
The Ministry of Foreign Affairs is currently not aware that any Swedes are among the injured or deceased.
Thailand has experienced similar tragedies before. In 2022, 14 people died in a fire at a bar in the eastern part of the country.
