since you own an apartment in BKK, I assume that you have got a different visa than a tourist visa. In that case, most probably the IO would not ask you to show cash.
More than likely similar pricing if you were to hurt yourself in Aus without Medicare and insurance. I’ve lived here for 18yrs and needed an emergency operation in Perth while back visiting. Gallbladder removal. By memory it cost me $11,000aud. Answer from @Jason Wheatley