Long term visa first ( you can use proof of assets
From your own bank) then agreements for permanent / rented premises and then go to the bank. This way no agent fees or the bank con if selling insurance
12 months as need to show consistency of earning. Money has to go into Thai baht to prove you can support yourself.
For you I would go for the deposit. I understand you can earn interest now. You can withdraw during the year but put back 3 months before renewal. Easiest way is to leave in and place in an interest earning account