I've noted the posting below regarding eating at the Bangkok airport....I'm in a similar situation, although I'll have a total of 6 hours between flights. (So, really, perhaps, around 4.)
I have heard of a Aw Taw Kaw market not (too) far from BKK. I've heard conflicting reports regarding whether or not it's open during the week, though.
Any suggestions for good chow given my long layover?