You would not be applying for a visa - you would apply for an extension of stay based on marriage, and this extension must be renewed each and every year. Additionally you will need to report to your local immigration office every 90 days.

@Oksana **********

if they are looking for a solution prior to leaving their home country,

they could consider obtaining a non imm o-a multi entry visa. That would give them a year before needing to deal with anything Thai Immigration related other than the 90 day checks. And if they did a border run just prior to the enter before date that is stamped on the visa they could get a second year as well.

Some state that this is a difficult, complex, expensive visa to obtain and I suppose that depends a great deal on the specific Thai Embassy/Consulate you would be dealing with. I have gotten a number of these visas over the past few years and have never found them particularly problematic nor expensive.

They would be applying for an extension of stay based on retirement and not a visa. I think they need to apply at the immigration office that services the area where they live vs picking and choosing an office. I have not heard of differences in prices between immigration offices.