National police spokesperson Trairong Phiwphan said the attack took place in Debsirin Nonthaburi School in the Bang Kruai district on the northwestern outskirts of Bangkok on Friday. The suspected gunman was also dead, he said.
In a statement, police said the suspected gunman also shot and killed his grandparents at their home before opening fire at the school. The suspected perpetrator was identified as a student but no further details were provided.
Police said the shooter fired at least 26 bullets, and was found with 34 additional ammunition rounds. The gun had belonged to his grandfather, police said.
Al Jazeera’s report said students had identified the gunman as a teenager who was enrolled in the school.
Public broadcaster Thai PBS reported that three teachers and three students were killed in the attack, according to Al jazeera.
Prime Minister Anutin Charnvirakul offered his condolences and said he had ordered relevant officials to take care of the victims.
MNA