This was my third stay at Galleria. The staff are always excellent.
For the most part, the rooms are clean, comfortable, dark and quiet. If you look closely under the bed and in the corners though, the cleaning is less thorough.
The gym is small, one treadmill of average quality, one crosstrainer of dreadful quality, a bike I didn't use and enough weights. The pool is great for swimming laps and has always been a nice temperature.
The shuttle service to the Sukhumvit is very handy.