Following the fire report at 8.30am, Pol Captain Rattanaporn Boonhansa of Phratunam Chulalongkorn precinct went to inspect the Patama salon and spa in Soi Rangsit-Pathum Thani 7 in Tambon Prachathipat along with firefighters and five fire engines.
They found black smoke bellowing from a three-storey commercial building.
The fire was extinguished, but not before the first and second floors were destroyed.
Salon employee Nanthaporn Krasang, 30, said there was smoke coming from inside the building when she came to open the salon as usual at 8am and so alerted the authority.
The cause of fire was under investigation on Friday.
Salon owner Alongkorn Mangkorn, 53, told police he expected fire damages to reach Bt10 million as the salon and spa had many pieces of expensive medical equipment required for the cosmetic procedures it offered.