careful, not sure about Thailand, but some countries require you to show the local passport if you have multiple nationalities regardless of where they stamp the entry. I come from a Suth american country, every time I go home I can enter with my European passport but still required to show my latin American passport. Maybe Thailand can be the same.
Maybe read the BOI guidelines first, I don’t think small companies apply. The investment I think was very high last time I checked. Small companies can’t apply for BOI, or at least it is my understanding.
Nope, you would need an international drivers license that explicitly says you can drive motorcycles. In your case it would require category A. You only have category B.