What steps should I take to obtain a retirement visa in Thailand after arriving?

Get a o a visa in your country before you go

There's no "multi" retirement visa available in Thailand. A re-entry permit is a totally separate thing.

You don't say WHAT entry stamp you'll come in on so we'll go with you're either coming in with out any thai visa in your passport or on a single entry tourist visa.

Once you get here, GO immediately to your immigration office and file a TM30 <- notification of foreigner in residence form (to prove you live where you say)

Then get the hand out from your immigration office listing the documentation required to get the 90 day Non-O visa based on being over 50 (retirement). You HAVE to get that before you get a year extension and a re-entry permit

Works like this

- apply for the 90 day Non-O visa (when you have between 15 and 21 days left on your entry stamp depending on the office you use) for 2000baht

- wait the under review period - 14 to 20 days

- go back get the Non-O visa and a new 90 day stamp inked in

- wait until you have 30 days left on that stamp

- apply for the year extension for 1900 baht

- once it's inked into your passport apply for a multiple re-entry permit 3800baht

Be aware that you are better getting a single entry Non-O in your home country first, then applying for the extension here. If you apply for the single entry here you will have to prove that the 800k was transferred from abroad.

This is a general guideline