The three other Potanthus species in Singapore all have FW spots 4 & 5 of equal size & abdominal end almost wholly yellow in the male.(female may have a bit of dark dorsal shade.)

P. omaha males.
http://www.butterflycircle.com/check...obby%20Mun.jpg
http://a4.pbase.com/g4/25/686825/2/1...1.Buz1tBHC.jpg

P. ganda male & female.
http://4.bp.blogspot.com/-L3ew9ztkIk...thus-ganda.jpg
https://3.bp.blogspot.com/-e_HuBihng..._underside.jpg

P. confucius. males.
https://wingscales.com/content/record/515-1-738e1.jpg
https://wingscales.com/content/record/514-1-f6975.jpg

TL Seow: Cheers.