During the regular working day every Immigration can issue re-entry permit to anyone regardless of where they reside or the extensions was granted. On weekends the border can issue, but it is up to them.
Hoffmann Sukanya, at least quote from where you got the info. BTW, this is the most important piece of info: "The Non O X visa does not replace the current annual retirement extension".
as long you just stay a few days each time you will not have a problem. You can always show the return ticket, hotel booking and money. They pull you out if they see you max every 30day entry stamp.
for a person over 50 years of age this is not a good advise, IMHO. If you quality you can get a O-A which is good for a stay of up to 2 years. Or get a Multiple O , this is good for a stay for up to 15 month. Or just a three month Non O and do an extension inside Thailand.
I got this link from a person that went successfully to HCMC. As Steve Greir said correctly most people just go to Savannakhet/Laos which is just opposite of Mukdahan to get the yearly multiple there, based on marriage, without showing funds.