5% is I fear an overly conservative estimate for Thai banks. Last week I checked at BBL and the highest rate they offered was 1.625% on a fixed 9 month deposit - leaving 3 month for seasoning in an accessible account.
Would love to hear where you can get 5%.
On another note - using multiple OA visa's (every two years) you'd never need to have money in a Thai account, nor for that matter have to season money in an account - just have when applying.
I would say with only one setv and one visa exempt entry you've a fair while before it'd be considered "extensive" history of using tourist type entries.