Police said the deceased, identified as Siwat Phannikorn, was being held under a Phuket Provincial Court arrest warrant on charges of attempted murder and carrying a knife in public without reasonable cause.
Pol Lt Kriengkrai Daokrachai, Deputy Investigator at Thalang Police Station, said officers were alerted to the incident at about 12:17pm after the duty officer discovered the suspect unresponsive inside the cell.
Senior officers, forensic police, a public prosecutor, district officials and a forensic doctor from Vachira Phuket Hospital attended the scene to conduct an examination.
Police said Mr Siwat was found in a seated position after using a trouser drawstring to hang himself from the iron bars inside the detention cell.
Initial examination found no signs of assault or struggle, and investigators estimated he had died less than two hours before his body was discovered.
CCTV REVIEWED
According to police, three suspects were being held in the cell at the time.
The two other detainees told investigators they had been asleep for about two hours before officers entered to provide food and found Mr Siwat in a secluded corner of the cell.
CCTV footage from inside the detention area reportedly showed all three suspects inside the cell at about 11am, with Mr Siwat appearing restless before moving alone into the corner where he was later found dead.
Police said officers and detainees discovered the body at about 11:40am.
Mr Siwat had been arrested on Wednesday (May 13) under Phuket Provincial Court warrant number 418/2569 in connection with an alleged stabbing attack on April 25.
Police also said he had a history of drug use and previous arrests for disorderly conduct and property damage.
Thalang Police confirmed that a full investigation is underway because the death occurred while the suspect was in police custody.
The case has been registered as post-mortem examination case number 52/2026.
CCTV cameras continuously recorded events before, during and after the incident, and the footage would form part of the investigation, Thalang Police noted in their report of the death.
The family of the deceased did not raise any objections during the initial post-mortem examination, police said.