Can immigration see your bank account?
Can immigration see your bank account? Excluding countries with mass surveillance, then generally no, they cannot see your bank account. Such surveillance would first of all require the immigration to have a deal with all banks for all countries passing through.
Can customs see your bank account?
Yes, of course they can ask to see your bank account. And they can search your luggage, your cell phone, your social media accounts and your laptop computer too. The alternative, should you object to those searches, is to give up your attempt to enter the country and return home.