There's no Thai consulate in Thailand. I'm sure if you go to your local immigration office they'll give you the list of what's needed to apply for extension based on retirement.
I went to several banks last year they say no. Then asked an agent ( Siam legal) who wanted 14,000 tbt! So I went next door to Bangkok bank with a Thai speaker and we got it done eventually.
took me one visit to find out what hoops to jump through because I was on 30 day exempt entry, then return with the stuff they wanted. 2 hours doing the process and sorting out the two ID problem. ( I only had one ). But I had help from a Thai speaker who helped get it all done.
Something that shows you're in the country you're applying from if you're applying for a visa. Maybe like in UK a council tax bill or bank statement if that's where you're applying.
I did it on a visa exempt (extended to give enough days), I have a condo and someone who spoke Thai helped me. They didn't tell me about insurance till I'd done everything. . I was so annoyed but after an hour waiting, leaving and coming back next day with extension, an hour doing application, I didn't want to leave without my account. 5,000 tbt ins, no need to renew this. The only thing that was a real problem for me was 2 forms of photo id.