Insurgents armed with automatic rifles sprayed bullets at a new police station building in Sai Buri district in Pattani, where investigators later collected 75 spent cartridge cases.
The police station was attacked on Friday evening. Duty officer Pol Sgt Natthawut Surat was severely wounded and later pronounced dead by a hospital.
A bomb disposal squad and Border Patrol police thoroughly checked the police station compound on Sunday. They collected 75 spent cartridge cases from four types of firearm - M16, HK33, AK47 and AK102.
Forensic officials were examining the spent shells for leads to those responsible.
Police did not say why their "thorough inspection" was left until two days after the attack.
The targeted police station was still being completed and was not open for use. It still lacks some walls because the funding ran out, Thai PBS reported, adding that there were at least three attackers.
