Police are seeking four teenagers in the assault of a ninth-grader during a gang fight in Sattahip.
The 15-year-old victim suffered a broken jaw and swollen head when he was hit with baseball bats and steel bars March 1 at a bus stop in front of Sensiri flea market.
Police initially arrested a 15-year-old former friend of the victim and expanded their investigation to three other teen boys from Ban Amphur who joined in the attack.
Police said the former friends had a long-running dispute and the gang leader waited until graduation day to settle the grudge. The victim was with four others, who fled before being hurt, but the victim was lying down, playing with his telephone, when he was set upon.