Angel Dominguez: Great modern art museum, photos allowed. Mostly Thai artists with some international pieces on top floor.
Torzin S: Elegant modern designed museum with a lot of Thai artists' masterpieces. Great place for contemporary art exhibition and surprisingly late 19th century european paintings.
kwik.buck: Not the Tate, but great Asian modern art museum and architectural building. Worth a visit.
4sq Thailand: Jim Thompson's House, which is built in traditional teak wood style, is now a museum displaying valuable collection of Thai arts such as benjarong (a multicoloured porcelain).
Eleni Miliou: Amazing place. Impressive traditional Thai architecture, a wide collection of century old antiques and Thai art, beautiful gardens and ambience. You can watch live silk-weaving and traditional dance!
Ilya Gerasimov: Must-see poi of Bangkok. Great example of Western-Eastern art and architecture fusion done right.
MJ The young witch: Great place to hang out with friends, for the shows, arts, and drinks!
Sasapin Siriwanij: Chill in the cafe from 3pm til midnight and check with the staff whether any cool art event is ongoing :)
Littlelalunta: Another fine space for arts, drinks and gigs!!
DHR.com: Constructed under King Rama V, this grand Renaissance building (now a museum) has great frescoes and traditional Thai arts and crafts inside. Located at Ratchawithi Road, Dusit. Open daily.
Lhing Mai: Visit "Art of the kingdom" 150 baht only! Worth a lot more than what you pay. Appropriate attire is required!!
Arno Wolter: Magnificent pieces in the museum. Truly art of the kingdom. Don't miss it! While you're there visit vimanmek mansion as well.