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In order to get a O retirement visa you would have to show 800,000 BHT in you bank account for a period of 2 months before you apply got O visa. If you do not meet this financial requirement then you can get a Thai visa company to do for you but it will cost you up to and maybe more than 30,000 BHT

About 30,000 BHT and up to over 65,000 BHT

I did it by bank transfer from my bank at my country to the Bangkok Bank in USD. The Thai bank changed it to BHT. If you not aware the money has to be in your Thai bank for 2 months before and 3 months after you apply for your visa. Minimum balance after is 400,000 BHT which the next year you have to show bank book statements for the last 12 months

Two months before and three months after then balance can go down 400,000 BHT. If you apply in Thailand you will have an O visa. If outside Thailand it will be an O A visa

Bring your passport and photos and 300 BHT. You may have to show them where you live. You will get this document at Thai Immigration. It is valid for 30 days. You submit your documents and come back later that day or the next day depending on when you go.

The extension you apply for in Thailand for 30 days. It used to be you can apply for another 30 days before the first extension runs out. I am not sure if you can apply for a second 30 day extension. Check with Thai Immigration

You will need Fit to Fly Certificate to show to boarding agent in Lisbon and you will have your paperwork check again in Dubai

While in Thailand you should carry with you your passport with your visa in it just in case you get stopped for what ever reason.

One or the other. Easier to have 800,000 BHT in your Thai bank account. 2 months before and 3 months after. Minimum balance 400,000 BHT. More work the other way but possible