Even if it's SGD, if they're on local (SG) contracts then factor in the lower tax rate and you're not doing too badly; probably more in hand than someone getting the same number in AU. It's all paid gross (tax is paid in the following year, by the taxpayer) with no super / pension deduction (if you're not a citizen or permanent resident).
NN is correct, a foreigner does then have to make their own arrangements for health cover, schools, pension etc. and cars are excruciatingly expensive, but SGD 240k / year can buy you a fairly reasonable lifestyle in SIN city.
Put it this way, a single-earner household in Sydney can find it tough on AUD 240k / year, after the mortgage, car and kids; same in Sing. You probably wouldn't be far ahead, but you probably wouldn't be too far behind, either.