The Burmese Sailor (Neptis leucoporos) is one of the several black-and-white "Sailors" in Singapore, and can sometimes be confused with the Common Sailor (Neptis hylas) or the Short Banded Sailor (Phaedyma columella) when in flight. 
These butterflies have a distinct weak gliding / "sailing" flight which is different from the other black-and-white genus Athyma species, which have a more robust and stronger flying pattern.
The wings are black and white above, whilst the undersides are grey. 
This distinguishes it from the Common Sailor, which has a rich golden brown underside.

This is the subspecies Neptis leucoporos cresina occuring in Singapore.

Pulau Ubin, Singapore, 24 October 2022