There has been an article referring to an economy class lounge at the airport
and another mentioning of such facility, here
Bangkok economy class lounge
Economy passengers on Thai get the rare treat of access to a lounge at the new Suvarnabhumi Airport. Indeed, it is rare among airlines, most of which operate only First and Business-class lounges, except for Bangkok airways (which has a lounge for all on the other side of the airport). It sure beats sitting on the hard metal benches in the airport concourse.
True, the lounge isn't brilliant. But Thai is following a trend at other new airports which have started offering economy-class lounges. There is plenty of seating, showers, a telly showing Thai films, and free internet access.
But I can not confirm where to find such lounge. Is this information incorrect or no longer true?