I always use cardless ATM withdrawals now. If you're with Kasikorn you can also use Bangkok Bank ATMs. But it's best to also carry the plastic card as well because you never know, your phone could blow up.
in Thailand if you open a bank account in a particular branch it will always remain in that branch even if you move to a completely different area. You can change your address with the bank but the account will always stay with the home branch.
In practical terms that means if you move to a different province you will pay a small commission for ATM transactions because your account is still at the home branch and always will be unless you close it and open another account in the different province.