
The fire broke out at the boarding-house of Pithakkiart Witthaya School in Wiengpapao distirct at 11 pm, police said.
The girls who perished 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.
After the blaze broke out officials could only evacuate a few of the girls while the rest were trapped inside.
Channel 3 reported that most of the victims were burned beyond recognition.
Scientific Crime Detection Division officials were dispatched to investigate the cause of the fire Monday morning. The victims' bodies were sent to a hospital for victim identification procedure.
Sawang Momdee, the Chiang Rai chief disaster mitigation officer, said disaster mitigation officials, rescuers and police combed through the boarding-house trying to locate the two missing girls.
The Wiengpapao district office provided a shelter and basic necessities for the survivors.
The private school is run by the Patthakit Suksan Foundation and the school manage is Rewat Wassana. Most of the students are hilltribe girls from Chiang Rai and Chiang Mai.