Mung is a slur used to describe Vietnamese in a derogatory way. Vietnamese people that were relocated to America by the US government during and after the Vietnam War. It's actually the correct pronunciation of the word "Hmong", mountain-dwelling people inhabiting southeastern China and the northern parts of Vietnam,
The word Mung is a racial slur that has been used historically to degrade and dehumanize vietnamese. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to vietnamese. If you are unsure about whether or not it is appropriate to use the word Mung, it is best to err on the side of caution and avoid using it in any situation.