Handed that letter both at check-in, and it was also in the suite when we arrived. First time guest at GH Erawan.

The dark glass building to the right of the picture looks to be the Renaissance. Another option for these with SPG Plat since that's now Marriott Plat, which gives you breakfast at the Flavors restaurant, club access with breakfast, tea, canapes and drinks (liquors available were at a lower level than GH E), 1 free laundry item per night, 20% off F&B. However, their service is inconsistent, with some great employees mixed in with the meh.