I had done SIN twice before doing both SIN and BKK on an award trip in early September (actually flying from SIN to HKT as part of the award).
I love SIN because it is so easy to get around in. The first visit, at this time last year, was my introduction to Asia. I had been nervous but found everything easy. While it may not be as "chaotic" as BKK, I still find it charming. Since I'm not big on museums and would rather walk around and see architecture or gardens, I had a good time.
BKK was a bit like a whole other world. I stayed at the Conrad and found it easier to get around than I thought. I definitely didn't spend enough time in BKK to get a full taste, but enough to know I'd like to go back (unlike KUL which I've put on the been there, done that, got the t-shirt, and I'm done with it list).