As I'll be in Hong Kong the week before Korea, I can always pick up one of these
http://www.beecrazy.hk/en/deals/seou...-local-postage
S.K. Telecom / 8 days / 5GB data / HKD $150 ..... ~ 23,426 won
http://www.hk.chinamobile.com/en/cor...ming-data.html
7 days / 5GB data / HKD $155 / ~24,185 won / I can use remainder data in HK.