Try Kayak.com. It’s a portal that gives you a broader look across 6-8 booking sites, but sometimes I don’t see Agoda.com listed and that website can have better deals in Asia. But before booking a place, I will always check the hotel’s own website as they can have better packages or even a better cancelation window especially if it is a resort type place.
Of course kayak.com, booking.com, agoda.com, priceline.com are all owned by the same company. Then you have the “expedia.com” group of travel owned sites.