The catch is that only American Express is accepted at the moment. Apple Pay’s launch in Singapore was originally announced in October 2015 for a rollout in 2016, and sure enough that has happened. This seems to be a similar situation over in Australia where Apple Pay only works with American Express cards.
Apparently banks in Australia have been resisting Apple’s attempts to get on board. It seems that the banks aren’t too happy about how they helped lay the groundwork for NFC-based payments, and Apple coming in and encroaching on their businesses. We’re not sure if it is the same situation in Singapore, but the country has allowed NFC-based payments through a local card called EZ-Link.
In any case we can only assume that eventually Apple Pay in Singapore will open itself up to more credit card providers in the future, but for now if you don’t own an American Express card, you’d be out of luck.