Aha, there are 2 different visa's they call long stay. The non imm O-A indeed, but here we talk about a non imm. O, so without the 'A' ! That's maybe the misunderstanding. With the non O-A you immediately can stay for a year. Also 1 extra year with a border hop just before that first year expires, when you have y'r healthcare insurance covered for that year.
I think there is a bit misunderstanding between the words 'Visa' and 'year extension'. When you have a visa (non imm. O), you can enter Thailand for 90 days. When you entered, y'r visa is void. It gets a stamp in red 'USED'. So you don't have a visa anymore. To get this visa in y'r home country, you can use y'r home country bank for income verification. After e.g. 60 days in Thailand, you ask for a year extension at Thai imm. The first time you do this only then you need 800k฿ in a Thai bank account. But it also has to be there already 2 months before ! So when you enter Thailand, you have to open a Thai bank account as quick as possible and put 800k฿ in it. Then, if you want to change it to 65k฿ a month for the second year extension instead of the 'locked' 800k฿, also start transfering (international) 65k฿ a month. Then this second year extension you can use (bankstatement) these 12 transfers of 65k฿, to get it and only then you can take out y'r 800k฿.
Watch out. 12th is a Thai holiday. Also watch out, you need a re-entry permit (form TM8) to keep y'r year extension alive when you come back. Also can do this on the airport but need some more time.
"In my time" (already living in Thailand for 7 years), you had to show 2 or 3 last bank statements and income statements to get my non imm O (Which still was a sticker and I had to go to the Thai Embassy). Don't remember the amount. So sorry, cannot help you with what they want for proof and/or amount now.
Should be on y'r Thai Embassy site I guess. Well, good luck anyway.
Well, it says 'intended' so you must have an idea when you leave within 90 days after issue date of this visa. Same with return date. If they ask fo uploads, maybe a self made little paper with 'going for year extension' concerning return date will do. Because indeed a non O normaly does not need a return flight. The money however (banked or income) would be a bigger concern I guess.
No, it is a year extension from 1 march 2025 to 1 march 2026, a so called extension of stay. This is no visa anymore. I would not take the risk with the former re-entry permit. If it goes wrong, you have to start all over.