It would be the same in the UK if the motorbike rider, had no license or insurance, he would lose the claim, we don't know the Russian just might be 100% legal, I have known a couple of English guys walk away from an accident because the Thai's had no license and the police could not do a thing about it,
One accident I know of years ago a farang hired a truck and had accident with a minivan full of farangs doing a visa run, none of them had insurance, the rented truck or the minivan, the police tried to stick it on the farang with the truck, he didn't know it had no insurance when he hired it, and that minivan had been all the way to Sadao and back with no insurance,