On most airlines you can only use the lounge of the airline you are flying with regardless of class of travel. There are exceptions made for frequent flyers with elite status e.g. with *G you can use any *G lounge provided you are travelling with a Star Alliance airline.

But China Southern and Korean Airlines (I assume that is who K.A. is as KA is actually Dragonair) are part of Skyteam, not the Star Alliance.