Was India actually known for seafaring?
Apparently, this kinda sorta might have happened IOTL. It was probably due to some isolated castaways during the Indus Valley Civilization landing in Northern Australia though, since a formal colony would have resulted in the transition of more cultural elements, including agriculture.
^ There was no particular reason for Britain to settle it either, given a larger and much more fertile continent closer to home.
A settlement around Perth could arise either spontaneously by exiles, or proactively by a South Indian maritime empire seeking to dump its undesirables somewhere. After a few decades, word of rich gold deposits in the Outback will inevitably draw a rush of gold diggers, many of whom will stay.
An empire in which Malays and Dravidians had equal status would not really be able to dump its undesirables in *Indonesia. Australia might be a handy dump for a continuing Chola Empire with such a context in mind.
Why not, though? There are huge unsettled tracts of land in Borneo. The malay peoples of Indonesia IOTL were still in the process of settling beyond the coastlines of Borneo, for example, and even with the modern Indonesian resettlement programme, much of the interior is still barely populated.
Prison camps or settlements in the Bornean interior make much more sense than spending money shipping undesirables further off.
South east Asia is not only settled by Malays but almost all are under austronesians stock. Borneo was never predominantly Malay until recently. The natives in Borneo are more sea faring than the Indians in otl. There is little difference between Borneo natives and the Malagasy in Madagascar.
Going back to be the op, it would be more likely that Australia would be colonized by people from south east Asia than Indians. However, Hinduism and Indian culture spread in south east Asia otl. So it may be an austronesian civilization but with Indian influence like a Hindu Javan kingdom, etc.