I think the previous posters are trying to answer your question, but you aren't quite catching it. Bangkok Air has its own lounge in BKK for all economy passengers. The *A lounges are not accessible with the UA Club membership if you are not departing on a *A flight (a bit different than the using the UA Club card in the US). Bangkok Air is not affiliated with *A. (I have been inside the economy Bangkok Air lounge at BKK - don't waste your time.)

If you are departing from BKK in Bangkok Air business class or premium economy, you have access to the Blue Ribbon lounge, with showers, etc.