I've been living in Chiang Mai for several months now
I went to a travel clinic before coming here, and was advised by the doctor to get vaccinated against the following (I ended up taking all of them except for Rabies):
Hepatitis A & B (3 shots)
Japanese Encephalitis (2 shots)
Tetanus (1 booster shot)
Malaria (weekly pills)
Typhoid fever (oral)
Cholera (oral)
Rabies (shot)
I skipped Rabies as it was expensive and the risk was fairly low. Just have to make sure I don't get bitten by dogs or bats. The doctor said that if I'm mainly in the cities, I should be fine. But if I'm going to be spending a lot of time in the country side, I should definitely take the shot for Rabies
You should check with your government's official travel advisory for a list of recommended vaccines (this is State Department's)