On my last trip to Bangkok I went to five rooftop bars: Banyan Tree Vertigo Moon Bar, Sofitel SO Park Society Bar, Millennium Hilton 360 Bar, Lebua Sirocco Sky Bar and Above Eleven.
My first stop was Vertigo Moon Bar located on the roof of the 61st floor of the Banyan Tree Hotel. BKK traffic is a nightmare so your best bet is to take the MRT to Lumphini and then grab a taxi for ~150 baht to the hotel. Ask anyone in the lobby and they will point you towards the bar elevator. Once you get to the top make sure you specify that you want drinks (not dinner). Try to get there early so you can get a seat near the edge.
Banyan Tree is the second highest rooftop bar in Bangkok (Sirocco is the highest) and it was significantly less crowded than Sirocco. Banyan Tree is a very dark bar and not the best place to take pictures. I found the vibe very relaxed and Vertigo was my second favorite rooftop bar. All of the rooftop bars in Silom are packed with tourists and westerners. Thai people are noticeably absent, probably because drink at Vertigo costs about 5x more than it would 60 floors below. Quite a surcharge for the view.
Vertigo wasn’t overcrowded, had a great vibe and a decent view. One thing about all the rooftop bars, the view gets old pretty fast. You’re too high up to people watch and there aren’t many things to look at after dark. Lebua Tower/Sirocco and its golden dome being the obvious exception. If you’re in BKK, you might as well check it out, but I wouldn’t recommend staying in the hotel and I doubt you would want to go more than once. Here’s a look at the drink menu, cocktail list and prices.