You need to link your HSBC accounts, in other countries you can do this online, but in TW (ofc) u need to go to a branch and fill in a form to link that up. Do yeah, u must have HSBC account at both ends.
Once the accounts r linked, you can access the global view and trasfers of the accounts and send instant free transfers (as long as you have premier status) in major currencies (TWD cannot be transferred outside of TW, so u need to convert into like USD/GBP/EUR/other and then have a corresponding currency account in your other HSBC.
Unfortunately u can’t do global transfer via app in TW, you need to log in on the website