According to the Nation newspaper, the fire broke out at the boarding-house of Pithakkiart Witthaya School in Wiengpapao district at 11 pm Sunday.
The girls who died in the fire were between five to 12 years old.
There were 38 schoolgirls staying at the boarding-house. They came from hilltribe villages in Chiang Rai and Chiang Mai to study in the town.