A Samut Sakhon factory recycling used lubricants caught fire late on Wednesday, badly damaging the building but no one was injured.
Dozens of fire engines and a large number of firefighters were used to combat the fire, which was fuelled by large quantities of petrol stored inside the factory, and it took around three hours to put it out.
The factory, which is 30 metres high and located on a five-rai plot in Muang district, is owned by SJ Oil Co.
Police are investigating to determine if the business was operating without permit.
Department of Labour Protection and Walfare director-general Panich Chitchang said there were around 20 employees at the factory but the fire occurred outside working hours.
The owners would be charged if they were found to have ignored safety measures, Panich said.