Bangkok has a number of rooftop bars and the Octave is located in central Bangkok on top of the Marriott Hotel. The views are spectacular and the pricing at the restaurant is in line with other rooftop bars in Bangkok. Their cocktails are great and Happy Hour is from 5-7pm being a 2 for 1. Absolutely stunning views of Bangkok on the top floor and it really is on top of the roof of the hotel.
If you want to hangout with friends and watch the sun set over Bangkok then this is a great place to do it at. Go nicely dressed. The drinks are not that expensive and the service is perfect. The DJ is excellent, the atmosphere deep and chilled and there is no dedicated dance floor.
There are a number of other rooftop bars in Bangkok and the closest one to the Octave Rooftop bar is the Red Sky bar which is not too far away. There is also the Skybar which is has a great river view at night as well as the well known Zeppelin Bar in Bangkok. The Octave Rooftop Bar is well worth the money and one of the best in Thailand. The bar is close to the BTS Thong Lo station in Bangkok.