Thanks to anyone who can share some insight. I did some google/flyertalk search and got mixed answers. I am booking flights for my mother to from MKE to KHH. This is the route I would like book for her (3 separate itinerary).
MKE to SFO w/ Southwest (paying cash).
SFO to HKG w/ Singapore ( First class using Krisflyer miles transferred form Chase UR).
HKG w/ Dragon Air (Business class using BA miles)

My mother holds taiwan citizenship so she is in the America w/ traveling visa. I understand she will have to take her luggage and re check in at SFO. My question is does she have to go through customs at HKG or just security check. Also will Singapore Airline work w/ Dragon Air to transfer the baggage.

Thanks again if any can share some insight or experience!