The appropriately named Moon Bar is perched high atop the Banyan Tree Bangkok, which gives it the best 360-degree panorama in Bangkok. You can lounge around the sofas and low-lying tables with a drink. Come a bit before sunset to get the best seat, and don't forget to pack a camera, the views are staggering. If the weather is clear, do some stargazing with the bar's telescope. If the weather's bad at all, the place will be closed.
Banyan Tree Bangkok, 21/100 S. Sathorn Rd., Bangkok, 10120, Thailand