This is the very rare Neptis sedata.Correction:Probably just N. leucoporos.
The markings are practically similar to Neptis leucoporos but the ground colour is darker, black.
The abdomen lacks the white band seen in N. leucoporos, it being replaced by a greenish shiny patch.
TL Seow: Cheers.
PS. There is an observation from Singapore which is N. leucoporos but the abdominal band is white in a side view & green in a top view. https://www.inaturalist.org/observations/216732688