Original French parachute trousers in the 1947/52 pattern. As a former French colony there was a lot of French equipment and uniforms (and influence) in Vietnam especially early in the US deployment. The indigenous troops in the airborne units wore a mix of French and locally produced uniform, including the famous “bulletproofs” (also known as pinks or purples). US SF types would wear these types of clothes to emphasise their difference to the rest of the army, and also to add an air of mystery or BTDT (Been there, done that!). These uniforms would usually be used as base or party uniforms, and not on operations.
Photos courtesy of the Hall Collection.