Wow, Nokia just published new apps to allow Lumia users to redeem gift card with value of SGD 45 to get any paid apps in Windows Phone store. Quick grab yours here:
Follow the instruction shown in the apps, and wow, $45 just credited to my Microsoft Account wallet.
* Update: Just realize it is mentioned selected Lumia model only, so you can try yours. I use Lumia 1520 and redeem mine succesfully.