Why not convert the SGD into an AUD term deposit account with one of the AU banks here in Singapore. Sure the rate will not be great and you may lose out on some further AUD devaluation vs SGD, but at least the interest will be 100% tax free in SG. That can turn a 7% return into an effect 10-11% return depending on your AU tax status.
If you are a non resident for tax purposes in Australia you will only pay 10% withholding tax. You will find that the onshore banks are paying better rates than you can get here even taking this into account