You serve?

I'm sat in a tuk tuk, taking advantage of the chance to read. As the traffic comes to a standstill at a juncture a man in a sarong approaches the vehicle and says 'roi navee' - I take this to be Singhalese and don't look up from my book. He repeats it and draws closer, making it clear from his stoop and bent that he is speaking to me. I look a little closer to weigh up his mental state.
He tries a third time, 'Royal Navy? You serve?'
'No.'
He almost recoils. Backs off and the traffic unloosens itself with a guff of petrol fumes and we pull away.
I am dressed in a turquoise t-shirt and brown shorts. Not very naval to my knowledge. My doppelganger is afoot once more.