On seinfeld which bank did Kramer try to bilk out of 100 for not saying hello?

Kramer didn't try to bilk a bank out of $100 for not saying hello. That was a different episode where Kramer tried to get $100 for not saying hello to a cashier at a diner.

The bank episode you're thinking of is when Kramer tries to get $100 from a bank for a "lost" $100 bill, claiming it disappeared during a deposit. The bank teller is suspicious and calls security, but Kramer is able to escape with the money.