The vehicle was burnt and dumped at an abandoned well eight kilometres off the scene where the mayor, Sama-ae Doloh, mayor of Piyamumung tambon administration organization of Yaring district was shot dead.
Police said they believed the vehicle was hidden by the gunmen somewhere in a village after the shooting to prevent police hunt.
It was then driven out at night to burn and dump at the well to destroy evidence.
Initial examination showed the vehicle was not on the list of stolen vehicles. It was bought from a second car dealer and its annual registration has not been extended for several years.
Police said they would summon the original owner of the vehicle for questioning to find out if the attack had any link to southern insurgency.
Sama-ae Doloh was driving his pick-up truck to his office in Yaring district when another pickup truck gave chase until it caught up with Doloh’s vehicle.
Then three masked men riding on the back opened fire with their assault rifles at Doloh, killing him behind the steering wheel. Eyewitnesses said that one of the gunmen disembarked from his vehicle and walked toward Doloh’s stationary truck apparently to find out whether he was dead or not and then left quickly.
Police said they were not sure whether the mayor was killed by southern militants or not because the victim used to be an influential figure in the tambon.