What are the considerations when applying for a retirement visa in Thailand through an agent in Pattaya?

Get a non O visa (90 days) in your home country. Open a Thai bank account when you arrive - no issue if you have a non O visa. Go to your local IO to find out their specific requirements for a 12 month extension and then apply.

Easy. No need to use an agent for anything.

Does my bank of America account count if I get my account transfered to the bank in Chiang mai

How to obtain a “90-days Non-Imm-O retirement/over 50 visa” inside Thailand and the subsequent 1-year extension of the stay permit based on retirement

This requires careful planning, because it needs to be timed correctly. It would be best if you already had a Thai bank account with 800,000 THB in it opened during a previous holiday, if you wish to go this route.

You can surely do the “Change of Visa Type” from a 60-days visa-exempt or a 60-days tourist visa, to a “90-days Non-Imm-O retirement Visa” on Immigration, if you got all your ducks in a row

But that means that you need to open a bank account immediately after you entered. And the clock is ticking away!

Right after you entered, you need to open a bank account and transfer from abroad a minimum of 800,000 THB. For the application to the “change”, there is no seasoning needed, yet.

You will however need proof that the 800K came from abroad, so take care it is coded correctly as FET by your Thai bank

EXCEPT in Jomtien/Pattaya, there the 800,000 THB need a 2-months seasoning period for the application to the initial visa! That’s what makes Jomtien a Catch22

On a visa-exempt, you will definitely need to pay an agent service to open a bank account for you, don’t waste any time trying to do it by yourself

You also got the option to use the "income affidavit" from your Embassy in Bangkok, confirming a monthly income of no less than 65,000 THB. as a Dutch citizen, your embassy in Bangkok is still issuing it

The U.S, U.K. and AUS embassies have discontinued issuing income affidavits, so as a citizen of these countries, you would need the 800,000 THB deposit in the first year

Visit your Immigration and apply for the "change" to a "90 days Non-Imm-O Retirement Visa". It will be issued 15 days “under consideration”. That’s why you need a minimum of 15 days left on your stay permit. After these 15 days, visit immigration and pick up the visa stamp.

The application fee is 2000 THB. You will need a rental contract on most Immigrations. You will need to be TM30 registered.

The 90 days visa will start on the day you initially applied for the change.

Beginning from up of 30 days before the 90 days stay permit will expire, as soon as the 800,000 THB deposit has been sitting in your Thai bank account for 2 months, you can apply for the "1-year extension of stay permit based on retirement".

You will need a bank statement for the 2-monthd seasoning, and pay a fee of 1900 THB.

READ the instructions explained in the web-link I provided carefully.

The “retirement” option is number 9. Click onto it, a .pdf document from Immigration will open. Carefully go through it as it lists the requirements.

If you want to play ultra safe, visit Immigration right after you entered, and ask them for the requirements for a “change”, because some Immigrations apply their own rules which might differ slightly from the police order.

You've already made up your mind. An agent will get you a bank account and a visa, if you qualify. So go ahead and spend a few thousand baht to do it that way

Better get your visa in advance. Switching is for when you planned to go for a short time and your plans change.