The explosion occurred in front of Ban Taba school in Tak Bai during a routine patrol by security officials to give protection to teachers.
As the patrol police unit passed by near the school, a bomb hidden was detonated, seriously injured ten.
Two of the seriously injured are father and a 4-year-old daughter.
All were taken to Tak Bai hospital where the father and his daughter died upon arrival.
EOD team was called in after the explosion and traffic on the road in front of the school was sealed as security officials feared more bombs might be planted in the vicinity.
By late this morning, traffic was still closed as EOD team was searching and clearing the area.