you are to be commended on the completeness of your post and research. The big gap is that he doesn’t have his UK motorbike license and yes, he doesn’t have time to get it. Unfortunately this may be a tough lesson for him to do his preparation more thoroughly. There comes a time in our childrens lives when we as parents can no longer help and he must stand on his own two feet.
Your last paragraph will win you no friends in Asia. It is disrespectful. They have no obligation to help you get to Thailand. If you don’t like what they offer stay where you are.