Quoting from a news clipping back in December
There's no entrance fee, and the museum is conveniently located right next to the MBK shopping center and Siam Square, so the only excuse for not visiting there would be to be outside Bangkok. Which is sadly the case for me, when I will come to Bangkok this exhibition will be over - hopefully it will have something interesting then, but cannot find any schedule of future exhibitions on the BACC website. Maybe I can still get the exhibition catalogue for this one in two month to have at least an idea what I have missed.
The ‘Bangkok 226’ exhibition depicts historical facts of the 226-year-old Thai capital through various kinds of art including paintings, photographs and sculptures.
The collection created by over 50 contemporary Thai and foreign artists is divided into 4 parts. Beginning with ‘Bangkok Early Day’, visitors travel back to the era of King Taksin who founded Bangkok 226 years ago and view old Siam maps. [...]
Rather odd for a museum photography is allowed, so there's a photo gallery of this exhibition on Narm's multiply page. My favorite painting is theDemocracy Monument reclaimed by nature, the picture above I have "borrowed" from the ThailandQA forum.
By the way, it seems like the BACC website is still under construction (it even says "temporary website" in the header) not unlike the museum itself, which has several floors still empty and waiting for a permanent exhibition. Especially the English section of the website clearly needs expansion, as this venue was built be for tourists as well.