Sirocco, (outdoors) on the 63rd floor in the luxury hotel, Lebua, in the State Tower skyscraper, is right next to the river. The nearest sky train station is Saphan Taksin.
The Roof Top Bar in the Baiyoke Sky Hotel is a covered bar, located on the 83rd floor of Bangkok’s highest skyscraper. As an added bonus there is a rotating viewing-platform on the floor above.
The Vertigo/Moon Bar (no roof) on the 61st floor of the Banyan Tree Hotel, has a feeling of being on a plane.
Red Sky (outdoors) is in the Centara Grand Hotel, Central World, in the shopping district, on the 55th floor.
The Three Sixty Lounge can be found on the 32nd floor of the Millennium Hilton Hotel by the river.
Remember that most bars require you to be suitably dressed. Google the names for their addresses.
Buy Baht, THB, from FOREX Bank before you leave.