Flashing your licence is likely to result in the check in staff rolling their eyes at each other and making fist on forehead signs as you turn and leave!
Politeness is far more appealing to them. Booking using "Capt" as your prefix can help too: I was upgraded from business to first 10 days ago with SIA.
The best way is to have a frequent flyer card and try and get to a reasonable level (Silver or Gold); they really do have some effect.