You won't need yellow fever, the only reason Sofi did is because she went to Africa. Don't bother with rabies either unless your likely to be away from medical facilities for a long period of time (unlikely).
Malaria: I would presume KayleeLand is referring to Larium which isn't usually advised as it has some pretty nasty side affects. Other popular medication are Malarone and Doxycycline. Malarone has the least side affects of all malaria medication, but is also the most expensive at around 1GBP per pill (you also won't be able to buy it anywhere other than the UK). Doxycycline is much cheaper but has worse side affects, and apparently the sun sensitivity can be really bad, so not recommended if you already have problems with sun burn.
I personally didn't bother. I spent loads on it before I went following the advice from my GP, but once getting there I didn't see a single mosquito the entire time in Vietnam so stopped taking them. Still have 70 Malarone tablets sitting in a draw somewhere... Even in Cambodia there were barely any mosquito's. Prevention is far better than medication, and more important since no drug is 100% safe.
You aren't at risk of Malaria in Thailand unless you go to northern hill areas (around Chiang Mai etc - but not inside Chiang Mai itself). You are at risk in all of Cambodia and Vietnam, and I'm not sure about Bali.
Vaccinations: You'll probably get given DPT (dipheria, Polio and tetanus), Hep A&B, and be asked if you want to pay for Rabies and Japanese Encephalitis. Both of those aren't generally required though, and its up to you - they aren't free, infact they are very expensive.
Talk to your GP, read about the risk on the internet, and way up the pros and cons. Take what your GP says with a pinch of salt mind, my one was a right scare mongerer.