have a look at the OA on the thai embassy website. It takes a while to get your ducks in a row as you need the police check & doctors note (which was the hardest thing for us to get) Don't apply too early as the click starts ticking once it's been issued.
Look at back packer insurance we used big cat as it's extendable if you stay more than 1 year, also don't forget to get an international drivers permit before you come, it'll only be valid here for your 1st 3months but it's a start.
Good luck, you'll love it. Feel free to pm me if you have any questions & no you don't need an agent!
The longest is an OA visa applied for in the uk is valid for 1year, as it's multi entry you can leave to a neighbouring country & return before the expiry date & will be stamped in for another 12 months assuming you have insurance for the length of your stay. With this method you get very nearly 2yrs & can keep your money in the uk if you want to.
The other option is a Multi Entry Tourist Visa which is valid for 6months for a 60day stay whuch can be extended by a further 30days once in Thailand after which you would need to leave & return. This would give you upto 270 days if timed right.
It is also possible to arrive visa exempt for 30days which can be extended by another 30. Again you can leave, reenter & repeat but only officially allowed 2 per year & I'd reccomend leaving for at least a few days inbetween.
Which is best for you depends on the funds you have availble & how long you want to come for. For a permanent move I'd reccomend either an O visa or METV then set up the bank requirements & do an extension based on retirement once you're here
Wise is undoubtedly better for smaller amounts while swift, bank to bank will have far cheaper fees for large amounts but you may lose a little on the rate.
Mist Thai bank accounts charge a landing fee, usually a max of 500bt. Also be aware that there is a limit on the amount you can transfer to some banks in Thailand in 1 transaction
Trailing spouse is possible, you would be advised to get your marriage cert legalized for use in Thailand by having it certified as an original which is done somewhere in Milton Keynes assuming you married in UK, but please google it as things change. You may have to get it translated into Thai & certified again here. This can be done in Bangkok or maybe by an agent if neccessary. Different immigration offices interpret rules differently so always best to check exact requirements with your local office.
Come on tourist & convert to O or O visa but work fast as you will need 800k in Thai account 2 months before your 1st 2year extension
get it certified in UK as it would have to be sent to Milton Keynes anyway. You can then get an agent to do the rest here if you don't want to mess about with the Thai embassy in the UK.
If you google legalizing a UK marriage certificate for use in Thailand I think you'll find some posts
Get your marriage certificate certified before you come, Milton Keynes I think. You'll then have to have it legalized for use in Thailand, either by the embassy in UK or in bangkok. To do trailing spouse you'll both need O visa & will then apply for extension as retirement & trailing