What are the best banks in Bangladesh that offer current accounts with the highest possible interest on balances, and how do leading banks such as Standard Chartered, HSBC, BRAC Bank, Prime Bank, and City Bank compare in terms of features and benefits? Additionally, given that most current accounts in Bangladesh are non-interest bearing or offer very minimal returns, what key factors such as fees, transaction flexibility, minimum balance requirements, and digital banking services should customers consider when choosing the best current account?