Anyways i noticed that the cabin crew changed from their inflight dress (what looked like more traditional thai clothing for the women, red jackets for the men) into more formal attire (purple skirts/jackets for the women, black jackets for the men).
This is normal for THAI, and was introduced 3-4 years ago. You get welcomed in a more traditional (less-work friendly) dress. Once, up and away, crew change into more practical clothing.