Okay, there's more than a little b/s mixed in to the story being related.
Jerrywade because you're a new poser
, err poster
let's get some terminology sorted out first;
There is NO retirement visa available inside the country at an immigration office, period full stop.
There is a yearly extension of stay based on being over 50 (called a retirement visa by every Tom, Dick & Somchai half-wit foreigner and dip-shit immigration officer alike).
You NEVER EVER renew that. You are granted an extension of stay for a year at a time (because that's the maximum extension ANY foreigner can get here for ANY reason). The next year before your extension expires you apply for another year's extension. The old one expires and you apply for a new one.
The ONLY place the word retirement comes into it is that b/s stamp they put on your extension. The thai wording of the extension based on being over 50 doesn't even use the word "retire", it says; "in the instance of living out the end of your life".
Be that as it may, I'll now answer your query;
If you are using the "verification of income" notary letter from your consulate to meet the financial requirements (65k baht per month) there have been more than a few verifiable reports where a couple immigration offices are asking that you also take the letter to the Ministry of Foreign Affairs and get it "certified" <- stamped.
Almost all the translation services scattered around the country can and do offer the 'certification stamp' from the MFA for documents. I'm calling b/s on what you heard or think you heard as it most certainly doesn't cost 20K baht to get that stamp on a document. Now as far as "expedited service", I got no idea what you're talkin' about, because the thai immigration's AIN'T the Ministry of Foreign Affairs. Those are whores from different go-go bars.
So to re-cap;
YES it is true some immigration offices (Jomtien being one) does ask that your verification of income notary letter also get stamped by the Ministry of Foreign Affairs. As does the immigration office in Nakhon Pathom too. It's just a couple, not everywhere.
NO; it most certainly doesn't cost 20K baht to get that letter certified by the MFA.
Any questions?