The gunman who carried out a shooting at Patongprathankiriwat School in Songkhla province has a long history of psychiatric illness and polysubstance abuse dating back to early adolescence, says the Office of the Narcotics Control Board (ONCB).
The 18-year-old suspect, reportedly in a state of psychological distress, opened fire inside the school after seizing a firearm from police, killing the school's director and injuring five students.
ONCB secretary-general Pol Maj Suriya Singhakamol said on Saturday the suspect first received psychiatric treatment at age 13 and had used multiple drugs, including methamphetamine, cannabis and kratom.
A review of national treatment records, conducted in coordination with Thanyarak Songkhla Hospital, Songkhla Rajanagarindra Psychiatric Hospital and Hatyai Hospital, found the suspect had undergone repeated treatment.
Between May and July 2025, he received ongoing care, but was referred for further treatment in August after showing signs of depression, erratic behaviour and a high risk of relapse.
Investigators found no drugs in his system at the time of the suspect's arrest, as he insisted that his last methamphetamine use was in late 2025.
Discontinuing medication in patients with a history of substance abuse could lead to severe relapse and loss of self-control, potentially resulting in violence, said Pol Maj Suriya.
Families should monitor warning signs, such as insomnia, paranoia, refusal to take medication or renewed drug use, and seek medical intervention immediately rather than confronting the individual directly, he said.
The ONCB, he said, would accelerate efforts to link real-time data on high-risk psychiatric patients, and urged the public to report concerns via its 24-hour hotline.
In another development, police in Songkhla are preparing eight charges, including resisting arrest, robbery, murder, attempted murder, unlawful detention, property damage, drug use and carrying a firearm in public, against the suspect.
Meanwhile, Provincial Police Region 9 commissioner Pol Lt Gen Piyawat Chalermsri has ordered an inquiry into how the suspect was able to seize a firearm from an officer during efforts to subdue him, leading to the school shooting.
The probe will determine whether the incident resulted from negligence or unavoidable circumstances, he said.
