Mun Poolsap, a 40-year-old building contractor, gave his account at a press conference held in Nakhon Ratchasima province yesterday amid high security.
He said he was driving alone on Aug 20 from his construction site in Pak Chong district of Nakhon Ratchasima and indicated to the vehicle of Farut Thaised, son of Chartthaipattana Party MP for Uthai Thani Chada Thaised, as he was about to overtake it on Khao Yai-Wang Nam Khieo Road.
After being overtaken, Farut's Toyota Prado flashed high beams from its headlights at his Toyota Vigo pickup truck. Mr Mun responded by shining spotlights on his truck back on Farut's vehicle.
Gunshots were then fired from behind his pickup, Mr Mun said, and bullets hit the truck. He said he let Farut overtake him and fired three shots from his 9mm pistol at Farut's vehicle, which lost control and hit a roadside power pole.
Mr Mun said he then sped off and threw his gun away in Ban Khanong Phra village on his way to go into hiding in Bangkok. He had his pickup repaired at a garage in the capital. Its damaged parts were replaced and fixed and its spotlights were removed. He then returned to work in Pak Chong.
He learned from the media that he had killed the son of the MP. Afraid he would be in danger, he contacted Pol Col Panu Buranasiri, deputy commander for investigation of Region 3 Provincial Police, and turned himself in.
He said he did not have enough money for a legal dispute with an MP, so he hoped the police would guarantee justice.
"I apologise [to Mr Chada]. I did not intend [to kill Farut]." he said.
Mr Mun insisted he had fired his gun in self-defence and had done so alone.
His gun is unregistered. He bought it from a man in Ratchaburi for 1,500 baht. Mr Mun is registered as a local in Chom Bung district of Ratchaburi.
On the suspect's pickup truck, there are six bullet holes in its console, right fender, right rear lamp, front right wheel, right headlight and left grille.
Assistant national police chief Pol Lt Gen Charamporn Suramanee said police intentionally released false information about the suspect's vehicle, saying it was a Mitsubishi Strada, so that the suspect would not be aware he was being tracked.
The police have not found the gun used in the murder case.
Mr Mun has been charged with premeditated murder and the gunmen who were in Farut's car will be charged with attempted murder. Pol Lt Gen Charamporn insisted police had not arrested a scapegoat.
Mr Chada, who was in a car in front of his son's vehicle on that day, said he saw two people in the killer's vehicle.