When you first enter Thailand you will be granted a 60days stays and you can extend for another month and that will give you 90 days in total. If you intend to stay longer like one year your best option is to do visa run and enter again with 60days and extend (another 90days) However the tricky part here if you do it again and they could see a pattern. You dont need a bank account but then again you will rely with ATM withdrawals of maximum of 30k baht plus 220baht fee or bring some USD with you that you can exchange once in a while.