However, for a DIY, independent traveler, Thailand is better. You can do nearly everything someone would be able to in the USA or Europe..you can rent a car and drive yourself. This is not possible in Vietnam, where self-drive car rental is unavailable.
I don't get that impression at all. Cambodian officers are usually surly, almost never say hi and don't like it when you lean into their window. They never have a conversation with you.
I prefer Thai officers BUT I will say that officers stationed at airports are usually not very friendly.
Vietnamese officers are downright rude - they'll throw your passport back at you. Forget about being greeted properly.
Lao officers are indifferent, except at remote land borders, where they can be quite friendly (but then again so are Thai officials at remote borders). It helps if you speak Thai/Lao though.
I get what you're saying (I know Vietnam well, spent some time living and working there and still travel there on business at least once a year) but less scams in Vietnam? My impression is there are more. That stated, things are improving.
I very much doubt they would care what address you put down. That's the most basic piece of information. As long as you write your name correctly and all other proofs you are asked to supply are attached, you should be fine.
The same dude who is adamant all countries are supposed to confiscate your driver's license when going for a driver's license in another jurisdiction. In fact, this only happens when you're applying for a driver's license in another state or province in countries with federal system of government and maybe the EU. It's not something the average country does.
You're not understanding the difference between ATM withdrawal charges on your end and the Thai end. There are two sets of charges and then usually a % fee applying to withdrawals in foreign currency too.
Very very few banks refund withdrawal fees - and even if they refund the foreign withdrawal fee on your end, they usually won't refund the 220 Baht fee on the Thai end. This is very rare nowadays because it's a major fee for banks and they're simply unwilling to absorb these charges.