Twelve suspected members of an organised crime gang were arrested in a police operation on Monday in connection with the fatal shooting of a student and a teacher in the Klong Toey area on Nov 11.
Thanasorn Hongsawat, 19, a first-year student at Rajamangala University of Technology Tawan-ok, Uthenthawai Campus, was shot in his chest and neck.
Teacher Sirada Sinprasert, 45, of Sacred Heart Convent School, was hit in the head by a stray bullet while she withdrew money from a nearby ATM.
The Nov 11 shooting at first appeared to be retribution, with the teacher as collateral damage, in a feud between students from rival vocational schools. However, further investigation by metropolitan police revealed that the shooter and his partner, who drove the motorcycle used in the shooting, were part of a crime syndicate with at least 84 members.
Later in November police searched for more suspects, arresting nine and also learning of a secretive LINE app room used by the syndicate.
Warrants were subsequently issued for the arrest of the three prime suspects - alleged shooter Anawin Kaewkeb, Abdulloh Dueramae, the motorcycle driver, and Noppawut Ruangsri, suspected of being part of the killer's team - and other suspects.
Police swooped in early Monday with 200 officers raiding 14 locations in Bangkok, Nonthaburi and Samut Prakan.
Twelve suspects aged 20-33 years were arrested, including a 24-year-old woman. They were charged with illegal assembly with murderous intent.
During the raids police seized two knives, a handgun, a box of .45 ammunition and 11 T-shirts with the logos of various vocational schools.
The three prime shooting suspects, all in their 20s, remain at large, with "most wanted" notices posted for their arrest. Police believe they are still in Thailand, hiding with assistance from other members of the crime syndicate.