I was accidentally at Nakhon Phanom and did ride up to the bridge to have a chat with some people there.
My question was of course "Can I cross the bridge with my bike?".
First guy said "No" but he was overruled by his boss who said "Yes, if you have passport for your bike".
So of course this is no guaranty that you can actually cross the bridge with your motorbike but there is hope ...
Now I always thought that you could not get an passport for your motorbike. But you never know ... so I want to the DLT in KK and "Mai mi pan ha" .... copy of the GreenBook, Copy of my passport, fill in some paperwork and pay 25thb. Now I have an plate from Chonburi so the big boss has to sign and of course he was not there but I can pick it up tomorrow in the afternoon.