Compare OTAs.
If you travel often, hotels.com has the simplest way to earn rewards. Stay 10 nights and the average cost for 10 nights will equal to a average cost free night reward. It is not bad.
Agoda's system a bit more murky.
See the analysis from this website. Also helps if your company needs you to travel but allows you to book from an OTA to rack up loyalty rewards/points.
http://www.roadwarriorvoices.com/2015/04/04/the-online-booking-site-with-the-best-reward-program/
Cheap is one thing but look at the rewards also. Why? You are SGer. We are an island. It is our nature to travel out. So rack up some loyalty points from an OTA to help defray the costs more for future travel.