I stayed on an earth room with Lumpini Park view. I didnīt get an upgrade, even though I booked through Visa Luxury Collection, which offers upgrades based on availability. It seems like Visa benefits arenīt really enforced or known as Amex Fine Hotel Resorts, as I also had to request mine U$25 credit.
The room was not pretty, but I liked its odd design. Lunch on Red Oven was excellent and spa massage, very good. I did post a review on Trip Reports page, but it includes a few other things not related to the hotel.
I certainly had a great stay there and would return.