To save you laying out for exit tickets. You can rent flight tickets really cheap apparently. Which of course you don’t actually use, but have them to show just in case. I haven’t gone down this route. But maybe other members can further elaborate on this?
It should be fine. Just make sure it’s all labelled clearly with his name on. Carry a copy of his prescription list (the one attached to his prescription). Carry on as hand luggage 😊
Better rates to change currency at the banks in Thailand. Just bring minimal amount of bht from home to see you ok for the first night and transport costs. 😊