Your PR visa only mean you can stay in oz. Not enter oz again, Holding you valid PR visa & off OZ, you won't allow enter again!!!!
Through, we need to apply for return back OZ travel visa if we want to go oversea and come back, you can apply for five years or two years return visa.
They can cancel your PR visa if "they think" you are not intent to stay oz.
( here is "they think", not you think)