Bangkok?
I know people have had mixed experiences with the new Bangkok hotel, but I was impressed with the swimming pool. It's on a reasonably high floor overlooking the river and across to the city. Quite fun to watch the frenetic activity from the calm of the pool. It's an infinity pool, with sun loungers sitting in the shallow of the water, which adds to the fun or feeling of calm depending on how you look at it.
But... when I was there the hotel was quite quiet, it's a small pool area and it could get overcroweded quite easily.
D