I have probably mentioned this a couple of times but everyone who lives in Singapore needs a ShopBack account - it is completely free to sign-up and if you do not have an account already, my referral link will give you S$5 just to register now. ShopBack basically gives you cash back for most of the purchases and transactions that you complete online. In the case of hotels, you will earn (and retain) your elite status while still getting a sweet bonus cash back so there is really no reason not to use it at all.
In case you do not already know, American Express is currently running a promotion (registration for promotion is required) which gives you a S$50 statement credit if you spend at least S$300 at a participating property. In fact, the promotion is pretty generous as it gives you this bonus per participating property - this means that you can earn the S$50 at the Conrad Centennial Singapore AND the Hilton Singapore both (there are over 60 participating properties around the region).
There is currently a 3% cash back for completed stay at a participating Hilton property worldwide (yes, this includes properties outside of Singapore as well) when use ShopBack to redirect you to Hilton. The final transaction is completed on Hilton.com so you do still earn your eligible nights and Hilton HHonors Points. Take the King Hilton Executive Room above for instance at S$270++ (Approx. S$318 after taxes) a night. Booking this room via ShopBack should earn you S$9.54 in cashback but more importantly, if you were indeed successful at registering for the American Express promotion, you will earn S$50 in statement credit. Taking all these 'discounts' into consideration, a weekend at the Hilton Singapore along Orchard Road will just cost approximately S$259 which comes complete with a night's stay, buffet breakfast and free-flowing evening cocktails for two.
More importantly, you will be earning Hilton HHonors Points and American Express Membership Rewards points with this stay. Since you are getting the cashbacks on the full amount, the stay at the Hilton Singapore can earn you up to 7,000 Hilton HHonors Points (assuming you do have Diamond status and have registered for the triple points promotion). Additionally, you should also earn 396 Membership Rewards points with your American Express card - assuming you are using the American Express Platinum Credit Card.