We've stayed at the Nasa before, and basically have done so on short layovers in Bangkok because a) it's cheap; b) it's clean enough; and c) most important, it's really easy to get to and from Suvarnabhumi Airport quickly using the Airport Link train. You ride four stops and head to Nasa Street, and if you take the right set of steps and escalators, you're right at the hotel entrance. Nothing fancy, and it feels pretty old and worn, but it's reliably "OK."