But I'm saying they cannot even get to our coastline. Singapore may be able to but they are an alliance partner. Indonesia, Malaysia, Thailand, Philippines, Vietnam, Cambodia, Laos, Myanmar and Brunei don't stand a hope in hell in transferring any realistic force on to Australian soil.
Secondly, as Placebo points out, any attempts to do such a thing would be noticed even just in the planning stages, should any of these countries even ever think invading Australia is a good idea to them.
* this was written before the post above me was edited. In response to that edit, Indonesia is likely to construct its military modernisation to defending its own territory and maritime environment with asymmetric conventional capabilities rather than creating expeditionary and long-range offensive forces. Not to say that we should be sanguine about our neighbour, more so that invasion of the mainland is not the top issue we need to worry about. We need to concern ourselves with being able to secure our own maritime environemnt and also protect our interests abroad in the maritime environment as well as in support of our alliance partners.