I don't really like discussing the relevant Aus vs Indo war, as it's absurd.
But.
Putting it very briefly, the RAN and the RAAF completely outclass their Indonesian counterparts in pretty much every department. They have better technology, better ships, planes, submarines, air systems and air defence and much more of them. Anyone that thinks a foot army wins a modern war is kidding themselves.
Most of indonesia's front line navy, airforce and tanks are upwards of 40 years old.
There's no possible way Indonesia could successfully invade Australia by sea without severe casualties, and trying to supply that invasion would be near on impossible with their current capabilities.
Australia's economy is in such a state, that if it went to war, what appears to be fairly insignificant capabilities, would go into overdrive. There'd be an influx of US and UK surplus planes, ships and tanks. The reserve would mobilize and conscription would be enforced.
The ADF inc. reserves at 100,000 strong mobilized would pretty quickly become 2-3,000,0000 in the case of an invasion.
The US is another matter in terms of allies, but Indonesia would be annihilated by the UK before a soldier set foot on this continent.