Once again I agree with Glen, if a country in South-East Asia wants to invade Australia it needs air-superiority over Australia’s skies, but it seems that Indonesia lack the capability to do so. At sea, RAN Collin class submarines could probably destroy the entire Indonesian fleet if ever deploy during an invasion.
The arms race in the region have nothing to do with attcking Australia, its a rivalry between the states and they all want military prestige over each other.