The International Airline Programme (IAP) for American Express Platinum Members is a great benefit if you tend to book Business Class (or First Class!) flights with partner airlines - and yes, Singapore Airlines is one of them! I think it is safe to assume that everyone knows about the S$1,712 annual fee that comes with the metal card but you definitely 'make your money back' very quickly if you use the perks that come with it. American Express has just revamped the main landing page of a website where IAP and Fine Hotels and Resorts (FHR) rates are accessible to Platinum Members.
The Platinum Card from American Express allows you to access FHR rates which will give you some really nice perks during your stay - all these rates are also elite-qualifying so you can still earn nights and points on these stays. The perks typically include a guaranteed late-checkout at 4:00PM (regardless of your hotel loyalty status) as well as a unique amenity which is typically a USD 100 property credit (perfect for one-night stays!). Additionally, the IAP Rates with partner airlines offer immense value when you are traveling in Business or First Class (there are also discounted rates in Premium Economy apparently but I have not looked at them into detail as I do not advocate traveling in PEY).
Book FHR and IAP Rates online here: https://travel.americanexpress.com.sg/