DOH - BKK (Doha)

Fellow Expats,

I would be travelling to Thailand during the second week of April and I need some advice on what's the best way to convert QAR to THB or to use a Credit/Debit card to withdraw locally.
I would really appreciate it if your suggestions are based on your travel experience.
P.S: I would be visiting Bangkok, Phuket and Pataya, so things to see and do recommendations always welcome :-)

Cheers!
Shane