First of all
I agree, at least 10 days per country, or stick to one area in each one. Tranportation is a problem, either they stop every where or they don't leave often enough, especially in Thailand and Camobodia. Tuk-tuk drivers start when they want (true!) and do not advise you when they do. So, you can sit in this tiny truck for one or two hours before heading to your destination !