witch hunt? no. I was told by my local amphur to have my passport verified and other stupid requirements for a yellow book!! That's not a witch hunt either - it's just plain stupid.
he said he will be here on a non o next time and will open a bank account and use it for retirement and wants to know the minimum required deposit for opening a bank account and will add money in the account later till it reaches 800k. You didn't get it - he will not open an account on a "tourist visa"
assumptions? That's necessary when you don't know what you've got. You said "I've got a 30 days extension on my non-o visa after 60 days" That's impossible. A non-o gives you 90 days stay permit - and can't be extended. So if you wrote correctly no assumptions needed. Apparently you are here - being a German citizen - on visa exempt (no visa) - which gives you 60 days and can be extended 30. You've already got an answer telling you if you can do it again.
you should learn to read!! He was not asking for the amount for retirement. He was asking for the minimum deposit for opening a bank account which is a couple of hundred baht. TRY to read the post again - maybe you get it right the 2nd time.