Ferry flights through Malaysia Thailand Indonesia Papua New Guinea - you should at least wear an iorned preferably white shirt & some crunchie bars if you have them. Indonesian's get very suss on you if you climb out of the steerers seat & don't 'look the part'.
Quite often travel agents in PNG will prefix a booking with Captain if the client happens to be an aviator & it may have something to do with the passenger list provided to the crew. I have seen hostie's walk up to a seat & ask the Doctor sitting there to come take a look at a crook geezer - how did they know that person was a medico?