as all the other posts say, you can stay for 60 then go immigration for another 30 then do a border bounce and repeat, if diving is what you want go to Koh Tao, message me mate I am a diving instructor
you don't need a bank account on exemption its just tourist until you decide after to pick a long term visa, only if you puck retirement visa you need to confirm to certain parameters
Your flights would cost that and then be homeless, Thailand is not a place that takes that kindly, try and get help at home and come up with a better plan I would say