The full moon party is absolutely fabulous, but unfortunately out of the way as u mentioned. It is not essential that u go to it, but if u can… do!
As for Northern Thailand, unfortunately I only experienced Bangkok and therefor cannot give u advice on where to go.
Japan and clubs. If memory serves me correctly then Tuesday is the day to go clubbing. Finding the clubs is another problem on it’s own. In Tokyo there is a district called Rapongi Junction where u will find a bunch of bars, restaurants and if u search well enough, a club or two. Beware though, lot’s of Nigerians and Americans there trying to get u into strip clubs where they steal your money. If u don’t know him don’t talk to him.
If you let me know where you are going in Japan I will try to find out where good clubs are since I have a couple of Japanese friends.
regarding the clothing question… As far as I could tell the Japanese don’t really mind what you wear. A pair of jeans and a shirt worked for my brother and I mostly wore cargo pants and golf shirts.
If you have any questions remaining feel free to ask.