Open the app on your phone, select "Cardless ATM" and login. Choose a pre-selected amount to withdraw or enter a custom amount. You then have an hour to find a BBL ATM.
At the ATM select "Cardless Withdrawal" then Bangkok Bank. It'll dislay a QR code and the app will prompt you to scan this code. Your cash will then be dispensed.
Choose an indoor ATM if possible as the sun on the screen can make reading the QR code difficult.