It is a female Pelopidas conjunctus.
The two larger species differs in that both sexes have a spot in FW space 1b (both sides).
In P agna & mathias, only the female have this spot.
Size reference.
P. mathias FW 16-18mm.
P. agna FW 17-20 mm.
P. assamensis is very large FW 25.5- 26.5 mm.
FW & HW with prominently white spots, large on the FW.
Antenna with a white band that goes nearly all round.
Females
https://www.inaturalist.org/observations/31291038
https://www.nparks.gov.sg/-/media/ff...46f461e50.ashx
Probable male.
https://www.butterflycircle.com/chec...0Ben%20Jin.jpg
Pelopidas conjunctus FW 21.5 to 23.5 mm.
Antenna with a pale area mostly on the underside & not prominent.
UnH spots are white but UnF spots are yellow & large.
Males.
https://www.inaturalist.org/observations/151597347
https://www.inaturalist.org/observations/19877822
Females.
https://2.bp.blogspot.com/-FvDO3Lfw_...lt_Khew_03.jpg
https://www.inaturalist.org/observations/155888799
https://www.inaturalist.org/observations/132122838
Much more common than P. assamensis.
TL Seow: Cheers.