@Michael ********
There are some offices Chaengwattana for one ( & it sounds like phuket is one too) that will not let people apply for a year extension based on marriage to a thai the FIRST extension (off the year O-A entry stamp).
They reason you got the visa based on being over 50 and you need to get at least ONE yearly extension for that reason FIRST before you can "change the reason" for your extension to one based on marriage to a thai.
What immigration office did you use
@An**
?