If you want to bring it back here (to Thailand) you will almost certainly have to pay import tax on it (even if it was Thai to begin with). Prices hold very well here with secondary depreciation almost nil (primary depreciation is wshenwhen it is first bought and goiesgoes from new to second hand - this is still low in Thailand) and prices hold for more than a decade easily on well maintained cars. Also, if it was a foreign model (i.e. not assembled in Thailand) then it would have had up to 400% import tax applied to its price when purchased.
All this means it will be cost effective to sell it here (Thailand) and buy again in Australia - you will probably be able to sell a reasonably new car (say 5 year old) and still make money after buying new in Australia (like for like models of course).
There is no ferry - it is half the globe away! Like a ferry to South Africa! Only way is to ship it.