Vaccinations for Thailand, provided you are not going to be spending too much time out in the jungles would be Hep A, Hep B (optional) and Typhus. If you plan on eating street food then Hep A and Typhus are good to get as you can catch both from improperly prepared food or water. Hep B is transmitted blood to blood, like HIV, but better safe than sorry and if you are getting Hep A, might as well get B. If you want to do a lot of trekking out in the jungles than malaria meds might be a good idea - check with your local travel clinic.
Good places to go - there are many - but here is the standard tourist rundown:
-Bangkok for temples and city life (Khao San Rd is the backpacker section)
-Chiang Mai for trekking, hill tribes, jungles, etc.
-Various islands for sun, sea, parties, diving, kayaking etc: Phuket, Koh Samui, Koh Samet, Koh Phangan, Koh Phi Phi - just to name a few - there are hundreds more.
Off the beaten path places - you have to discover those on your own!