I've been in all 4 of those countries, Thailand , Laos, Cambodia, Vietnam. I never got the vibe Americans were disliked anywhere, or that there's anything to fear from communists. That's old time American media and government BS. Vietnam is really more of a Chinese version of communist anyway, meaning it's really capitalist and everyone is mostly interested in making money. So if a cop pulls you in, it's because he thinks you will bribe him to get out. That problem is worst in Thailand. Of the 4, I prefer Laos because it's very cheap, not very many other. Mongers, pretty girl, less drinking. But they are all great places for this hobby. Personally I decide based on other factors, like beaches and tourism spots. But if you're heavy into the bar scene, pick Thailand or Vietnam.