Police have detained one suspect in the murder of Peera Tuntiseranee, the mayor of Songkhla municipality, but are still seeking five others.

Phaisal Nuphan turned himself in after a warrant was issued for him in connection with the drive-by attack on Peera on Wednesday night. He has been charged with being an accomplice in the murder.

Police accompanied Mr Phaisal to search his accommodation which is also the residence of Utit Chuchuay, president of the Songkhla Provincial Administrative Organisation (PAO).

On Thursday, a bronze four-door Toyota Hilux pickup truck was seized at a local radio station owned by former mayoral candidate Kitti Chuchuay, Peera's political rival and Mr Utit's younger brother. The pickup was suspected of having been used in the shooting.

Mr Kitti ran against Peera unsucessfully in the 2009 mayoral election.

Political conflict was the most likely motive for the slaying, police say.

Investigators have found that Peera, 54, had conflicts with several groups at his office, a police source said. He had suspended several municipal officials from their duties and expelled one deputy mayor.

For now, however, investigators are focusing on the municipality's probe into alleged corruption involving a former mayor, as well as its objection to a cable car project pushed by the PAO as possible motives for the killing, the source said.

After Peera was slain, police believe the shooters drove the Hilux pickup to the radio station, where they switched to another vehicle to escape.

Witnesses earlier told police that at least three attackers used M16s and rifles to shoot Peera.