There are not many old things to see in Bangkok, I was told. Only the grand palace and some temples are still standing. But still you can do quite a lot things here, shopping, dining, Thai-massage etc. On weekend you can visit the chatuchak market, if it gets too hot, you can go to Siam paragon, having some nice lunch and watching sharks in the water world (it is much easier to see sharks here than by diving yourself)...