If you are comfortable bringing it as cash, change at super rich (not all branches give same rate), deposit the baht you got at your bank.
You can check all the rates yourself to compare.
Of course, depends on the amount and where you are located to work out if the most favourable rate is worth any additional transport costs to get there.
----- edit added : after doing the math with the rates I found on internet, it turns out
Ministry of Foreign Affairs : "Furthermore, foreigners who enter the Kingdom under this Tourist Visa Exemption Scheme may re-enter and stay in Thailand for a cumulative duration of stay of not exceeding 90 days within any 6-month period from the date of first entry."
But : just because it is on their website, you can't trust that this is the law or how it is implemented...
Example : they also write about the visa exempt : "However, please make sure that you are in possession of a passport valid for at least 6 months, a round-trip air ticket, and adequate finances equivalent to at least 10,000 Baht per person or 20,000 Baht per family. Otherwise, you may be inconvenienced upon entry into the country."
Though they write that, any onward ticket will do, doesn't have to be a round-trip air ticket.
If you are Dutch, you also have the option of non-immigrant O-X for 10 years instead of LTR.
In my opinion, the yearly extension of non-O based on over 50 (retirement) is still much better value than either LTR or O-X. But maybe you could find it worth it - only you can decide what is best for you :
As we all know, div 1 has never heard about your special deal. So we're still waiting for your answer in this visa "advice" group, after more than half a year already. But as you admitted earlier : not a clue. (See previous screenshot).
So if not by bribery, what method did you personally use to circumvent the financial regulations ? Teach us something... Why did your passport had to go all the way up North instead of being handled at Koh Samui ? Sure there is a reasonable explanation. I must have been mistaken, therefore I humbly ask your specific method.