Hello, I am in hong kong for 2 days which octopus card should i buy ?

If you plan to travel by AE train from/to HKIA, you are advised to buy an Airport Express Travel Pass with two single journeys. In addition, you may ride on all MTR lines (except Airport Express, East Rail Line First Class, Lo Wu and Lok Ma Chau stations) within 72 hours after swiping it for the first time at the entrance gate.

Otherwise, you are recommended to buy a Standard Octopus Card, with which you can take MTR lines, Light Rail, buses, tram, ferries, etc. It is very convenient for you.