It’s free, air-conditioned, and right next to the Siam Centre, Siam Paragon and MBK. Comprising 5 floors of art (the current exhibition is a collection of prints from Japanese children’s magazines and other bits by artists like Chihiro Iwasaki) and a multitude of shops offering ice teas, clothing, or both, it’s a pleasant enough place to spend a peaceful few hours. Deposit your bag along with your ID card (or 100 Baht- they don’t accept passports, but will return your money) and head up to the exhibition on the very top floor
Even if you’re not particularly enthused by the arts, it’s nice to look at another culture’s interpretation of the human condition.
Small bottles of water are 15 Baht in the gift shop (i.e. walk to the 7/11 around the corner!). There are shops selling coffees, iced teas and food, and several places to buy things like jewellery, notebooks and bags (I also saw a woolly hat and mittens combo- really now?).