The iNat couldn't identify this sub-species though but this is a Catopsilia pomona crocale to be accurate.

遷粉蝶(Lemon Emigrant / Catopsilia pomona Form crocale)

Reference :
http://www.afcd.gov.hk/tc_chi/conservation/hkbiodiversity/database/popup_record.asp?id=2895&lang=tc
http://butterflycircle.blogspot.hk/2014/11/life-history-of-lemon-emigrant.html
http://butterfly.nss.org.sg/expert/200109-LE/200109-LE.htm