What are the financial requirements for the retirement O visa in Thailand if my monthly income is $1214?

You will not get an in country Non-O visa and year extension using the combination method (part monthly income and part banked money) you would need to bank the 800K baht for the Non-O and the year extension for the first year.

That's because you need to have monthly deposits from abroad, each month every month for the previous 12 months and just coming here you wouldn't have that which is why your only option is to use the 800K baht banked money method.

After that first year, when you did bring in 1200 USD a month each month every month for 12 months for your NEXT extension you COULD use the "combination method" (part monthly income and part banked money)

Let's do the math; 1200 X 36 baht to the dollar is about 43,000 baht a month,

43,000 X 12 = 516,000 baht, that means you'd need to bank 284,000 baht in a thai bank account in your name at least 2 months before you apply for the next year extension to show you hit the 800K baht for the year (516K + 284K = 800K).

The banked portion of the money would need to stay in the account for 3 months after your extension was granted then the balance could not go below 50% (142K baht) the rest of the year.

That's how the combination method works.

As I said you can't use it for the first year because you need 12 months of monthly transfers using monthly income to get an extension so your only option that first year is the 800K baht banked money method