There are two types of sub-wallets in ShopeePay which are Transferable and Non-transferable balances.
Transferable Balance
Please ensure that you have added a bank account to your ShopeePay account, then you can proceed with self withdrawal from the Transferable Balance by selecting Transfer to Bank > Add / Select existing bank account > Fill in withdrawal amount > Select Next > Select Transfer Now > Enter your ShopeePay PIN number.