He made the statement after investigators managed to salvage all 15 CCTV cameras at the residence of Praween Chankhlai, also known as “Kamnan Nok” – an influential figure in Nakhon Pathom province.
Highway police officer Pol Major Siwakorn Saibua was shot dead during a birthday party on the night of September 6 at Praween's residence.
The murder reportedly stemmed from an argument over a promotion. According to eyewitnesses, Praween’s alleged henchman, Thananchai Manmak, approached the dining table and opened fire on Siwakorn.
Surachet confirmed that the murder was premeditated because somebody unplugged the two cameras to prevent investigators from having a clear view of the murder.
It was hard to salvage the two cameras because there was an attempt to destroy evidence, Surachet said.
Investigators will summon all witnesses, including policemen and civilians, for questioning at the Provincial Police Region 7 headquarters in Nakhon Pathom, he added.
He said 13 cameras at the residence clearly show what happened before and after the shooting. However, investigators are still trying to salvage footage from the last two cameras found.
"All policemen [present] during the incident lied to investigators," Surachet added.
Investigators will request more arrest warrants on Saturday and Praween will not evade justice, he said.