I've only been to Thailand but I spent a month there so I saw a lot. Here are some thoughts (in no particular order) with a few links to more info on my blog:
-A lot of Thailand is blown up with young backpackers from Europe, Australia, etc. Some of the backpackers are cool but a lot of them are just traveling to get fucked up in new locales. I had a few nights like that but it's definitely not the reason I was traveling so I generally was on my own. If you can, try to make friends with locals or expats. They know the cool spots and generally care about more than just getting wasted all the time.
-Hitchhiking in Thailand is doable but not always easy. Locals probably won't understand what you're trying to do and might try to take you to a bus station. Having someone write a note out in Thai might be helpful. I met a lot of really cool people through hitching in Thailand so I would recommend it if you're not in a rush.
-You''ll probably start in Bangkok. Bangkok is super overwhelming but there's cool stuff to see there.
Khao San Road is a total shitshow but it's worth seeing one night.
The Grand Palace is kind of cool but admission is expensive and it's crowded with tourists so I would skip it if I were you. There are thousands of other temples to see in Thailand if you're into that.
-After Bangkok, you'll have to choose whether you want to go north or south. Most people go south to party on the islands but I went north to Chiang Mai. I travelled third-class on the train, which is pretty cheap. I stopped in a couple places in between Bangkok and Chiang Mai but there wasn't much to see besides more temples. If you go to Phitsanulok, there's a really great family I found through Couchsurfing that hosts travelers.
-I loved Chiang Mai so much that I spent several weeks there. There's a lot of expats around so there's a great art and music scene there as well as any type of food you can imagine. Every week there's a Couchsurfing meetup every Wednesday night at
Bus Bar that usually has cool people.
-People might tell you to go to
Pai after Chiang Mai but I didn't like it. People say it's a hippie city but it's really just another place for backpackers to get fucked up. There are some waterfalls outside of Pai that supposed to be cool but I didn't make it there.
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Chiang Rai is also pretty boring except for the White Temple, which is a really cool art project.
That's all I can think of right now. Let me know if you have any questions. Good luck!