Just starting the process myself Andy, although it'll be a couple of years before I'm there full time. Visas? Depends on your circumstances as to which one to go for.
Actually, being married to a Thai does give you more advantages than it used to. Previously anyone who's cat had been stroked by someone who'd been to Thailand could get a multi entry Non Immigrant O Visa valid for 12 months and do visa runs every 3 months. That is now reserved for those married to Thai's with a few exceptions. If you apply for an O visa from within the UK you will now have to show an income of around £1200 per month. I am reliably informed however, that no proof of income is required if you apply in Laos.
If you want to do without the visa runs, you'll need an O visa then apply for a 12 month extension in Thailand - in that case, I believe a single entry O visa is the easiest route. However, there are downsides to that route, depending on your particular circumstances.
1. You have to show an income of, I think, at least 40,000 baht per month or have 400,000 baht in the bank. I believe the income requirement is actually a joint income but some immigration offices don't apply that. 2. You will have to report every 90 days although I'm told that is soon to go online.
There is also the retirement visa option (OA Visa) but you need savings of 800,000 in the bank or I believe there is an income option on this one too - not sure how much it is. No visa runs but 90 day reporting and renewal every 12 months.
On both types of visa where you don't have to do visa runs, the rules are applied differently depending on which office you are applying to.
The above advice on O visas extended within Thailand is based on what I've been told when asking similar questions. I'm sure on of our ex pat members will be able to advise you more accurately.
For me, as I return to the UK regularly a multi entry Non Immigrant O Visa valid for 12 months is fine. I am never there long enough to need a visa run. I've had one for years although I couldn't renew it this year as I am no longer married and the copy of my ex's passport I have on my laptop has expired . That situation will be rectified shortly
I believe there is also a different type of retirement visa that needs visa runs - maybe someone else knows more about that.
Residence? I've always been told there's more chance of hell freezing although my lawyer in Thailand has citizenship now.
The Thai Consulate in Hull has a lot of information on applying from within the UK on its website but the rules seem to be applied differently in Thailand and in other countries.