@Tom ******
it's more complicated, requires more contact with immigration and may not allow you to use monthly transfers from overseas. Both require you to visit immigration every year but for marriage you then go through an under consideration period requiring you to return around a month later to get the 12 months stamped in your passport, for retirement it's all done on the day. For marriage you need photos of you and your wife in various rooms in the house and you also need witnesses (neighbours) to attest that you live together as man and wife. Many immigration offices won't allow monthly transfers from overseas for a marriage extension, you have to get an updated certificate from the amphur every year etc