Region 3 Provincial Police Bureau chief Panu Kerdlarppol said the suspect confessed to the fatal shooting of Farut Thaised in Nakhon Ratchasima on Aug 20.
The police commissioner said a press conference on the case will be held at the police bureau today.
The contractor reportedly turned himself in to Bangkok police yesterday.
The man, whose identity has not been revealed, went into hiding following the shooting incident that resulted in Farut's death.
Police said the suspect works as a contractor at a housing estate in Nakhon Ratchasima province.
Police brought the man to tambon Moosi in Pak Chong district of Nakhon Ratchasima where the crime took place for questioning.
The man was quoted by police as saying that he was driving his Toyota Vigo pickup truck alone, as Farut's vehicle approached from behind.
The suspect reportedly said that Farut's Toyota Prado flashed its high-beam headlights. He allowed the Prado to overtake his pickup.
Both vehicles then took turns passing each other and flashing their high-beam lights in anger, the man reportedly told police.
The contractor said the first gunshot was fired from Farut's vehicle. The man says he fired three shots back in self-defence before escaping.
The incident occurred on the Khao Yai-Wang Nam Khieo road in tambon Moosi.
The man went into hiding in his home province of Ratchaburi. His vehicle had bullet holes in it, which have been repaired.
He said he did not turn himself in to police earlier because he feared for his safety. The man was detained at the Region 3 Provincial Police Bureau that supervises Nakhon Ratchasima.
Earlier, Pol Maj Gen Ongart Phiewruangnont, chief of police in Nakhon Ratchasima, said the accounts provided by witnesses on Farut's side enabled investigators to narrow down the investigation.
Police detectives believe a 9mm pistol was used in the shooting.
Farut, 27, was shot in the head while driving his Toyota Prado with five passengers.
The shooting occurred during a family outing in Khao Yai.
Mr Chada and six members of his family, including his son, were staying at Chateau De Khao Yai Hotel and Resort in tambon Moosi of Pak Chong district. The shooting occurred after the group went out to dinner.
The seven members of Mr Chada's family left the resort in a Toyota Prado to eat at a McDonald's restaurant at Tesco Lotus on Mittraphap Road. Mr Chada met a friend who was waiting for him there.
After the meal, Mr Chada rode in his friend's BMW and Farut drove the Prado.
Police earlier offered a 100,000-baht reward for the information leading to the culprit's arrest.