The Supreme Court on Friday sent Kanpitak Pachimsawat, better known as "Mu Ham", to prison for 25 months for fatally ramming his luxury car into people waiting at a Bangkok bus stop, after a quarrel with a bus driver in 2007.
One woman was killed and three people suffered serious injuries.
In 2013 the Appeals Court reduced the lower court's prison term of 10 years and one month to two years and one month, and suspended it because Kanpitak had a "mental disorder" and his victims had already received compensation.
The Supreme Court upheld the 25 month prison term, but overruled the Appeals Court's suspension of the sentence.
The Supreme Court, its ruling read out in Phra Khanong court in Bangkok on Friday, lifted the suspension because Kanpitak had a long record of drug abuse dating back to when he was 17 years old, and despite this his father let him drive.
The court acknowledged that Kanpitak had self-control problems. He had shown a certain level of conscience when he initially went to drive away from the scene, but then he changed his mind and drove into the passengers.
Kanpitak, now 28, is the son of former Miss Thailand Sawinee Pakaranang and real estate businessman Kan-anek Pachimsawat.
On July 4, 2007, Kanpitak, then aged 20, had a quarrel with the driver of a No 513 bus in Bangkok.
He accused the man, Sathaporn Arunsiri, then 37, of hitting his Mercedes Benz car with the bus while in the Asoke area.
After a brief argument, both left the scene in their vehicles. Kanpitak followed the bus and when it stopped at a traffic light at Aree intersection, near Sukhumvit Soi 26, Kanpitak left his car and approached the bus driver again.
The driver then told his passengers they should leave the bus and wait for another one at the nearby bus stop.
Because the bus driver denied causing any damage to his car, Kanpitak hit him in the face with a stone.
Police arrived and put him back to his car. An angry crowd followed and hit the vehicle.
Kanpitak initially started to drive away, but then deliberately drove into the group of waiting passengers instead. Three people were trapped under the car when it came to a stop.
One woman, Saichon Luangsaeng, 42, a Bangkok Mass Transit Authority official, was pronounced dead at Chulalongkorn Hospital and three other people were seriously injured.
Kanpitak was charged and convicted of premeditated and attempted murder and physical assault.
In February 2015, Kanpitak's father Kan-anek, 64, was arrested at a hotel in Huai Khwang district, Bangkok, allegedly in possession of 1.07 grammes of crystal methamphetamine and drug-use paraphernalia. He was released on bail.