Whether you have built a 5-bedroom mansion on the river in Bangkok, or you rent a studio squat in the Khlong Toei slum makes zero difference to visas. You can get a "married to a Thai" visa which you will need to extend each year, and each year you have to prove to immigration that you're still married. Another option is a "retirement" visa, which is dependant on finances (either savings or income). Probably the best hassle free visa is the Long Term Resident Visa for Wealthy Pensioners, which is ten years multiple entry, and costs only 50,000 baht. It's the most hassle-free if you meet the criteria
If an agency cannot guarantee re-entry they won't take you. They look at your history first. A while back they were declining anyone with an ED or Volunteer stamp in their passport
They don't. I've done it many times. They're not interested in past history of 90-day reports. I'm in and out of the country 3-4 times a year, I seldom do a 90-day report