This is bordering on blashphemy, but the mall has some really good food. Sure, it's full of chain restaurants and stores you'd find in any mall worldwide, but the bottom floor has a sprawling food market with actual Thai food that's arguably better than what you'd get on the street for the same price. The sanitation and quality of ingredients is top-notch and there are so many different stalls that almost anything you want is available (although you'd be hard pressed to find cow udder soup and other Northern delicacies - try Laab Gai Baan Hong for that). It's a great place to sample lots of different Thai food in one convenient location.
Kad Suan Kaew, the other mall, also has a wide array of different local food but most isn't quite as good.