What is the process for switching from an O-A to an O Retirement visa in Thailand?

I have placed the TOPICS

Converting your

OA based retirement Visa to Non O retirement

And Border Run

And one year extension of stay as retired

On your post

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Other than your terminology mix up (there is no 45 day tourist visa on arrival 😮 ) you'd be comin' in on what's called a "visa exempt entry stamp" <- just a free entry stamp (for 45 days as long as you enter on or before Mar 31st)

There's no need to wait the 25 days to apply for the initial 90 day Non-O visa, you need a minimum amount of days (depending on the office you use) to cover the under review period (between 15 and 20 days)

Sounds like a good workable plan, you'll apply, pay the 2000baht, get the receipt that says when to return, on that date you show up, they stamp the Non-O visa and new 90 day stamp into your passport. Then you wait until you have 30 days or less left on that new 90 day stamp and apply for the year extension for 1900baht

Sounds about right. You must be able to show the money comes from overseas