Dear Alex and Julia,
1. What is the exact nature on the existing double taxation agreement between the Singapore and Australian Govt?
2. How does it apply to Australians working or/and investing in Singaporeans and for Singapore working or/and investing in Australia?
My knowledge is limited to Australian tax residents working as a salaried employee with a country that has a double tax agreement. My understanding is that for this person, e.g. Singapore salary income is NOT further taxed in Australia if all applicable Singapore tax has been paid. So where the Australian tax rate is higher than the Singapore rate, the taxpayer would only have to pay the lower Singapore rate, and that's it. (e.g. Japan has tax rates <20%, so I only paid that while working in Japan: I disclosed my Japanese income on my Australian return but was not taxed further on it).
This rule applies if, amongst other things, the person works in said country for at least 90 days.
I have no idea how it applies to Australian tax residents investing in Singapore. I suspect it doesn't. The employment rule is limited only to salary jobs (as opposed to, say, using a limited company to contract through). For an Australian tax resident there is no special exemption that I know of for foreign-sourced dividends, rent or interest. You will probably (not sure) get a tax credit for Singaporean taxes paid, but if the Oz rate is higher than the Singaporean rate, you pay the extra.
This is why the general strategy I outlined for working overseas assumes you don't invest overseas. I personally did not buy any UK or Japanese shares or property while overseas. I only bought Australian property and shares. It is especially effective if you have a net tax loss in Oz.
I have no idea how it applies to Singaporeans investing or working in Australia in any capacity, since I know nothing about Singaporean tax law.
Alex