I could see there being some form of honorific used in Cardassian culture, the way the Japanese use "-san", "-sama", "-sensei" etc, with different honorifics for different classes, stations, levels of authority, etc.
Considering that the Archon in "Tribunal" was referred to as "Madame Archon", (did I remember that correctly, or did I make that up in my head?) I would think that ma'am and sir wouldn't be too far of a stretch as a reasonable extrapolation.