I would start with getting an opinion about the work you want done from a surgeon in your country. See what he recommends. Then come to Bkk, see whoever you pick off the internet. See what he says, if you like the quack, then decide. Cosmetic corrections are not always possible the way the patient thinks. It needs an honest doc to tell the patient. There are guys everywhere who do the op regardless. If you have two opinions you can compare and decide. Afterall, you want to see improvement and not a botched nose and suffer another op.
Thai docs are no more qualified than docs in Oz. There are good, bad, greedy ones everywhere. I'm not sure if I would pick Bumrungrad as a hospital. My personal dislike. Most docs work in different hospitals, the fee changes with the hospital. Dont consider complaining or sueing Bumrungrad if your nose is not to "specification" after the op.