IIRC the new witness was killed in a motorcycle accident in the early hours of the morning, less than 24hrs after he was produced as a witness. Again, IIRC, it was several years after the Red Bull accident took place before the new witness remembered he had seen 'Boss' driving at a normal speed.
The other thing that came up was at the time the new witness died, his phone was removed from his body at the hospital by an aide who worked for the governor of Chiang Mai. Strange really, how the governors aide just happened to be at the hospital at 2am, when the body was brought in.