This is a shirt and trousers in the Thai Tadpole Sparse (Johnson classification) pattern, or Thai Tigers for short. One of the distinguishing features of the Thai patterns is their relative darkness (darker browns and blacks) than their South Vietnamese cousins. The black also tends to fade to a very agreeable dark indigo over time. This shirt and matching trousers still retain the deep black. The features are the same as for the South Vietnamese suits. The material is medium weight cotton.
Photos courtesy of the Hall Collection.