Well in Bangkok, I know many people who go there for holidays and I have to tell you with over 100+ Italian restaurants you can enjoy wonderful pasta, pizza, Risotto and etc. There's this place called "Zanotti" It's very expensive, but you get a beautiful dish, if you're looking for something cheaper you can always try Rossanos, it's cheaper and has very good quality meat and pasta.
I usually order Pasta Al'arrabiata or Pasta al Pesto.