One rescuer was killed and more than 60 people injured in an overnight explosion and inferno at a chemical factory that continued to send black smoke into the sky over Bang Phli district of Samut Prakan late into Monday afternoon.
Helicopters, some from the army, were called in to help firefighters spray flame retardant foam over the burning Ming Dih Chemical Co factory complex.
They were battling to keep the advancing flames away from further stores of chemicals at the site, and prevent another explosion.
Authorities warned of toxic fumes being generated by the burning chemicals.
Rescue foundations reported one of their firefighters was killed by the fire and 12 others were injured. Fifty other people were also hurt.
The initial explosion, which was felt nine kilometres away, damaged 73 houses and 15 cars in the nearby neighbourhood.
Thai Rath identified the dead victim as Kornsith Laophan, 18, who was killed as he and other volunteers were fleeing flames surging from a store of chemicals. He stumbled and was overtaken by the fire.
The Taiwanese-owned factory manufactures plastic foam and pellets.
The Disaster Prevention and Mitigation Department said the inferno began with an explosion about 3.20am. What set it off was not known.
Homes within a five-kilometre radius were evacuated amid fears of further explosions of the reported 50 tonnes of chemicals stored at the premises.
Firefighters and helicopters were reportedly trying to defend one particular area that held 20,000 litres of chemicals.
Pollution Control Department director-general Attapol Charoenchansa warned people that styrene monomer fumes from the blaze were carcinogenic .
The fire was about 10 kilometres from Suvarnabhumi airport, and the black smoke rising above the fire was clearly visible from there.
However, airport deputy managing director Krittiya Konthong said flights were not being affected.