Fortunately, I've received the needed ID copy last night after 5 months of troubles.
I've bought my Yamaha Virago 1100 from a British citizen who delivered the bike to me. Unfortunately, one of the biggest liars I've ever met and even having the green book, it was still in the name of a Thai lady.
The story was that his friend, married to a Thai, would come to Thailand on New Year's. But nothing happened and after more lies, I could find out that the lady who's the owner in the book had changed her last name and we also had her address.
We then drove a long distance, finally found the house, but we only found a relative who told us that the lady would be living in the States for quite a while. Good luck was that we had her on the phone, but didn't get an e-mail address, or similar.
As the neighbors had already mentioned, the man was an alcoholic and his promise to send us the needed document turned out to be a lie. One more liar wasn't really what I wanted.
He had the document which was sent to his phone, but he's just not sending it to me. After various phone calls and the promise that we'd give him some money for his help, he finally sent the urgently needed document and we can now put the bike in my or my wife's name.
I've done my research, asked my neighbor who's a lawyer and it seems to happen quite often that people steal bikes and cars with the papers and then try to sell them. Be careful and only give them money, once the vehicle is in your name.
We just renewed the tax and insurance and could change the name at the insurance company, but there was no way to get the bike in my, or my wife's name.
I had very good luck that the bike wasn't stolen and it will be in my name tomorrow. Be careful, especially when a bike or a car seems to be too cheap to be true!