Thailand:
It's systematic the way you hang out with girls there. You literally just pay pennies on the dollar for a girl to basically spend an evening with you. It's not prostitution because she'll just be like, "with" you. You can bone her if you want but it's not required or something.
Koh Samui is a great place for night life. If you ask a girl if she's a "real" girl, she'll be pretty honest about it. It's a great place for clubbing/bar scene and drinks are cheap. Just don't get too wasted and don't piss on peoples' cornflakes. If you're an angry drunk you might want to be on a one drink limit because you WILL get the shit beaten out of you if you act too stupid.
Chang Mai if you want to see temples and other cool stuff. It's also the best place for elephant riding.
Bangkok is mostly a hook-up place so if you want to get a discount on the fun life, go to Pattaya. They have a lot of amateur Muay Thai fights.
Japan:
If you're going to Tokyo, just remember that it's all broken up into districts. Akihabara is the tech area and it's where you'll find all the cool video games, action figures, comic books, maid cafe's and stuff like that. There's really fast WiFi there and a lot of cool shops to buy stuff at. This is where the giant Gundam is at.
Golden Gai bars - These are "foreigner friendly" bars. Basically bars that cater to people who speak English or Japanese as a second language. They're used to the more louder types but it still has a Japanese feel to it. Japanese girls also go here to pick up western men. Black Lion in Meguro and Footnick in Ebisu.
Shinjuku - This is mostly just a place to take pictures. Everyone there is in a rush to get to work and most of the skyscrapers there are just corporate buildings. It's about as exciting as going to Los Angeles and visiting downtown but with less homeless people who are hallucinating. They do have a good night club scene though.
Ginza is a shopping district that's more fashion oriented than Akihabara. If you want to pick up some swag gear, this would be the place to do it. It can be VERY pricy but the food in this area is pretty good.
Communicating with Japanese people:
Most Japanese people know a little English, are very terrible at it but are extremely conservative. It's very rare to make eye contact in Japan, even with people you sort of know. Meeting someone can be very deceiving because they will rarely say no to you when you ask something. It's YOUR job as the person asking to know what things you should or shouldn't ask for. A stranger in Japan will open doors for you, follow you to your hotel and help you carry your bags, if you ASK him to do it. Because to him, it's considered extremely rude to say no. But it's equally extremely rude for you to ask him.
My first Japanese girlfriend kissed me, dated me for three months and almost moved into my apartment. I didn't find out until after three months that she didn't even like me. It's just rude for her to reject or physically stop me so she just stayed quiet about it.
Japanese people WILL try to talk to you, to practice their English though. Also, if you're single and interested in Japanese girls, here's what I'll say:
There's three types of guys, as far as Japanese girls are concerned-
1) "Soshoku kei" - Herbivore men. It's a guy that's so shy and socially awkward that he never even speaks to women. One of the leading reasons for a low birth-rate in Japan and the reason a lot of Japanese women are attracted to western men. They're extremely shy and even worse, extremely sexist. This is the typical Japanese guy.
2) "Nikushoku kei" - Carnivore men. Pretty much the opposite of #1, this is the japanese equivalent to "thirsty dude". hits on pretty much everyone and this is what most Japanese women think American men are like. But this is preferable to the herbivore.
3) These are secret meat-eaters lol. They're guys who act shy but are secretly perverts. Women fear these types the most.
Overall, I would say you should memorize the following phrases-
"Sumimasen" - Excuse me, can you help me? I need your attention.
"Gomen..." - Non formal way of saying sorry, i bumped into you.
"Gomen... Amerikajin dakara" - "i'm sorry, it's because I'm American" This one is good because not only does it excuse you from basically ANY shit you do that's stupid, but people also think it's cute. I bumped into a girl and knocked her coffee out of her hand because of how crowded the subway was, and said this to her, she smiled and giggled and ended up showing me around the city (and dating me consensually later, unlike my first japanese girlfriend). A lot of shops excused me for not knowing yen/USD conversion or how to say numbers because of this.
Good luck!