Police said the fire stated on the second floor of the 6-storey building of Thai Saengfa Trading on Soi Phetkasem 31/4 in Bang Wa subdistrict at 5.30 am.
Fire fighters took about 15 minutes to put out the blaze.
Chamlong Pan-ek, 60, a security officer of the firm, said he spotted flames on the second floor, where a lot of electric appliances were kept, so he called the police, who immediately sent fire fighters to the scene.
Police have yet to investigate the cause of the fire.