This response may not be timely, if the OP has found the answer elsewhere or discovered for himself, but I will state it for the record anyway.

Yes, there is a fairly nice lounge used by SkyTeam airlines at Bangkok's new Suvarnabhumi airport. I believe it's officially designated as an Air France lounge on Suvarnabhumi maps and such, perhaps meaning that AF signed the lease, but one of the cardboard signs out front reads "SkyLounge," and it seems to be used by most or all SkyTeam airlines operating from BKK: AF, KL, KE, and SU. (I'm not sure about Northwest, but highly doubt it has its own lounge or made lounge-sharing arrangements with a non-ST carrier.) It is on Level 3, what I'd describe as the Mezzanine level, one level below the main "Departures" level/mall and one level above the gate areas used by both arriving and departing pax. You reach it by taking the escalator down from the depatures level at the junction of the E, F, and G concourses, then walk out the F concourse, and it's on the right. You'll pass a small BA lounge at the foot of the escalator, and Eva Air's lounge is opposite the SkyLounge.

The lounge has at least four rooms, IIRC. You enter in the middle. In front of you are circular tables of four workstations with some computers (few seemed to actually have working connections to the internet). To the right is a large room with a buffet station in the middle and a bar at the far end and lots of smallish cocktail-type tables. The selection of food was limited (nothing like KE's lounge at ICN) but still fairly good. Beyond the food-and-beverage room are the bathrooms; they had a nice modern design like everything else but ridiculously flimsy doors that felt like cardboard and must have been put up as a temporary fix (I hope) in the rush to open Suvarnabhumi by Sept. 28th. Turning left from the entrance is a standard lounging room with the usual modern comfy seats and small tables arranged in groups, and the fourth and final room at the end is similar, though it had a couple of massaging chairs naturally monopolized by two pax the whole time I was there. All of the rooms have floor-to-ceiling windows looking out on the ramp area of concourse G, and the room on the left at the end also has a view down the rest of concourse F. ^ ^ At night, the ramp is fairly dark, and the reflection on the glass makes it difficult to see anything out on the ramp, though it was a quiet night with not many planes out there.

The lounge dragons (who were Thai and very nice, of course) did not have access to KE computer systems, which was pretty unfortunate. They said they would make boarding calls; I left beforehand and so didn't hear it, but most of the lounge guests did turn up at the gate at the same time.

NOW... for the secret password. At Suvarnabhumi, the principal security checkpoints for departing flights are on the top level (the departures mall) right where that level comes to an end. Once you pass through security, you go down an escalator to the wide catwalks above the depature/arrival gates. From there, once you reach your particular gate, you go down to the gate level, where the gate desk and all of the seating is located, and you're penned in to your particular gate by glass walls. If a bunch of flights are departing from the same concourse around the same time, as was the case when I was there, the lines at the security checkpoints can get a little long and unwieldy. BUT... when you leave the lounge, you can stay on that level (do not go back up to the main depatures mall), go to the access point for your departure concourse, and pass through a security checkpoint on that level. On the other side of the mangetometers, you will find yourself at the beginning of the catwalks, and the crowds from the main security checkpoint will be coming down escalators to meet you on the catwalks. By doing this, you can save a bit of time and a lot of hassle.

I was there in the wee hours of Nov. 27 for a KE flight to ICN.