What are the steps and documents required for changing a retirement visa to a marriage visa in Thailand?

@Joe *******

it's just the way you're generally being approached by immigrations, and by the nonsensical rules they subject you to. They'll visit you to check if your marriage is de facto (not just legit). They'll interview people in your neighborhood to confirm your statements. If your neighbors are not home (but at work, to name an example) you risk that they cannot retrieve the required confirmation and have no choice but to reject the application. Friends of mine had to arrange that their neighbors stayed home on a particular day and they even had to supply personal docs of those neighbors as part of the initial application. The inspection visit also makes that you don't get the extension right away, but after a consideration period, requiring an extra visit to immigrations. And you can't go alone but you need to go with spouse.

@Bart *************

thank you your reply, yes they don't make it easy for us, I heard that immigration will come to the house and talk to the neighbours, we have friends on one side of us so hopefully that might help.