Can I extend a 90-day Non-Immigrant Retirement Visa in Thailand for an additional 30 days?

Your pension proof is your age. Its more than 50 years old.

F

you can only extend it for a year, but cost is the same - 1900 baht

You cannot extend the 90 days stay permit received when entering the country with a “single entry Non-Imm-O Retirement Visa” by the tourist extension of 30 days.

All you could do is exit Thailand and re-enter without a visa, if you are a citizen of a country that can get 30 days by entering visa exempt, you will receive a 30 days stamp and can extend this stay on Immigration once for 1900.- THB for 30 more days.

You can however, from up to 30 days before the 90 days stay permit expires, apply for the “1-year Extension of Stay Permit based on Retirement” if you fulfill the financial requirements .

. . . which are either a deposit of a minimum of 800,000.- THB on a Thai bank account in your sole name

or an income affidavit legalized by your embassy which proves that you earn more than 65,000.- THB per month

or, if your embassy doesn’t issue such an affidavit, a bank letter that proves you have transferred from abroad 65,000 THB onto your bank account, for 12 consecutive months, month for month

You can only extend a non immigrant visa for a year (unless you have a Thai spouse or Thai child.)

You can extension for 12 month or unless you can get your pension prove then 90 day ,