Yasuru Airport (KSX) skips the lounge question by simple necessity: this remote Papua New Guinea airstrip runs on demand-based light aircraft rather than scheduled airline service, so there genuinely isn't one to find here. Yasuru's grass runway is built for utility flying, connecting a remote community rather than hosting anything resembling a commercial passenger terminal.
Lae is the real pivot for anyone asking about actual airports in this part of Papua New Guinea. Nadzab Airport at Lae, on Papua New Guinea's northern coast, is a genuine regional hub with scheduled service on larger aircraft, and it is the realistic place to look for any airline facilities, connections, or premium-access options, modest as PNG's regional lounge picture is even there, rather than at a small strip like Yasuru.
The airline-service picture explains why Yasuru itself has nothing at all comparable. Flights into strips like Yasuru typically come from small regional operators and mission-aviation style services flying light aircraft on demand-based schedules, carrying passengers, cargo, and essential supplies to communities that would otherwise be reachable only on foot or by river, rather than from an airline running fixed timetables with connecting passenger banks the way any real lounge business would actually require to exist.
If your trip genuinely includes a stop at Yasuru, expect a bare airstrip experience: open-air or minimal shelter while waiting, no food service to count on, and boarding straight onto a light aircraft. Treat Lae as the actual planning point for anything resembling a terminal facility, and confirm schedules directly with the operator serving Yasuru, since demand-based flying in Papua New Guinea adjusts around weather, cargo needs, and passenger numbers rather than a fixed timetable, and the next available seat on the route may be several days away depending on the week, the cargo load, and the weather.