Staying at the Pathumwan Princess we just had to visit MBK, and when we did, we found some very cheap, traditional Asian food. Of course, if you didn't venture beyond ground level you could dine on familiar restaurants such as Maccas, KFC, and our favourite (for mid afternoon snacks) Saint Cinnamon. There was also a good all-you-can-eat restaurant near the supermarket.
Restaurants and fast food outlets could also be found on other levels, and the food court was on one of the upper levels. Worth hunting for it, as the price and variety was good.
Food was tasty and cheap, and the food court seemed clean enough to take a chance. We also found real coffee in a coffee shop on yet another level ... MBK is large! The hotel, alas, had not quite mastered the art. Acceptable, but the cinamon stick added little!
I used the rule of thumb and chose a meal that had to be cooked at high temperature in oil. Basically a stir fry with duck as the main ingredient. My wife made a similar choice. From there, it was off to the cinema (also in MBK).