A panel of prosecutors on Tuesday recommended charges of cocaine abuse and reckless driving causing death for Red Bull scion Vorayuth "Boss" Yoovidhya.

The dramatic turnaround on Mr Vorayut's fatal hit-and-run case in Bangkok in 2012 came from a review of the prosecution by a working group of the Office of the Attorney-General (OAG) and was announced by OAG spokesman Prayut Petcharakhun. Earlier a deputy attorney-general and an acting police chief decided not to arraign him on the charge of reckless driving causing death.

Mr Prayut said that Nate Naksuk, deputy attorney-general responsible for cases with justice complaints, had initially made a sound decision against arraignment based on available evidence and witnesses.

Although police investigators initially believed Mr Vorayuth had driven his Ferrari at 177 kilometres per hour, they later reduced the estimated speed to below 80kph. The change came after the suspect's repeated appeals for justice and more evidence and witnesses were gathered.

Mr Prayut also mentioned the account of late witness Jaruchart Maadthong, who reportedly drove a pickup truck at the crash scene at 80kph, saw the victim cut in front of him on his motorcycle and then heard the noise of a crash behind. The witness gave his story days after the crash.

Mr Prayut said that prosecutors' working group found later that Sathon Wicharnwannarak, a physics lecturer of Chulalongkorn University who worked for forensic police, had concluded that the speed of the Ferrari at the time of the crash was about 177kph. However, the conclusion had not been included in police's investigative report relating to the case.

The statute of limitations on the charge will not expire for another seven years.

Regarding the alleged cocaine abuse, Mr Prayut said that a blood sample taken from Mr Vorayuth's blood on the day of the crash indicated that he had used cocaine. However, police had not raised the matter in their past investigative report on the case, he said.

Police and prosecutors omitted the charge of driving under the influence of alcohol because a test showed the Red Bull scion drank after the crash -- because his blood alcohol level was so high, he would have been unable to drive. 

Mr Vorayuth, 35, also known as Boss, drove a black Ferrari that killed Pol Snr Sgt Maj Wichian Klanprasert, 47, in the early morning of Sept 3, 2012.

He crashed into the rear of the police motorcycle on Sukhumvit Road. He then fled the scene to his home nearby.