You can. But be aware that the immigration officer has the final say. If they think you’re trying to live there (which it certainly looks like you are) then they can reject you as you’re not a tourist. The visa exemption is for tourists.
If he has a British passport, he is currently on a 60 day visa exemption. If he leaves Thailand then returns, he will get another 60 days exemption. So, everything will be fine! Don’t worry.
She has made many trips this year. They could total over 180 days. Maybe that’s why immigration are getting difficult. And she’s visiting at least twice more this year. I don’t know how anyone can afford so many return flights in one year!
Consider alternatives to retirement visa. For instance, 60 day visa exemption then a 30 day extension. Near the end do a border run and start again. It’s not 100% as immigration may eventually stop you entering.
Other options are to pay an agent. They can get the 800k bank account requirement. Then transfer 65k each month into the account so you qualify for the second year.
If you can’t afford the 65k a month then perhaps just be a tourist. But residency would be useful.
Yes. I think he really needs advice on what visa he can qualify for that will achieve his objective of staying in Thailand almost permanently. He could do it simply with 60 day visa exemption plus 30 extension, then a border run and keep repeating this. It’s not 100% but suits a small budget.