not sure whether this is really a scam, maybe just a bit a overinterpretation of security rules

I usually just buy a bottle of wine upon return to Thailand (uneless I am coming from somewhere where it is less expensive). King Power prices for wine are by no means a bargain, but they are less than what I regularly pay at Tops/Central etc... for the same or comparable wines. I have never felt at risk for any kind of scam, but will avoid the skincare/fragrance areas where it sounds like this incident referred to above occurred. And furthermore, for those items the duty free prices are not substantially less expensive than department stores, if at all.