The Coach Boutique Hotel Sukhumvit 14 Bangkok
Located in the city center, with convenient transportation. Although it's in a small alley, there's a department store right across the street, making it very convenient for dining, entertainment, and shopping.
The breakfast provided is very rich. The three of us were full with just two portions. You can also have breakfast, swim, and work out in the rooftop garden, with plenty of activities to enjoy.
Unfortunately, the room doesn't have a bathtub, and there's a bar downstairs, so it can be a bit noisy at night.