Recommend an itinerary for a trek up to Chiang Mai?

Hello. I'm a 26 year old backpacker. Flying into Bangkok on Thursday. Meeting a friend in Chiang Mai on the Monday for a couple of days. That leaves me 4 days. Looking for some suggestions on a cool route up to Chiang Mai. Will take the train or bus. I'm very outgoing, and would rather be in places that I'll find other backpackers in. These will be my first days in Thailand. Any help would be much appreciated. If there are any sites that I should check out please forward. Thanks!