As people have told you. To obtain a Retirement extension you first need a Non O visa 2k baht. Then to get the extension 1,900 baht, you have to have 800k in a Thai bank account or prove an income from overseas for the previous 12 months of 65k.
I have a yearly income of 130k but not 800k in a Thai bank. I simply use agent who for 12,500 baht get you a totally legal extension within 3 days.