DTV for 5 years on soft power but you will still need to work something out for the last 3 years to get you to 50, you can get the platinum privilege (10 years 1.5m baht unless its changed) or LTR (however requirements are steep for the LTR)
Yes but make sure you keep to the terms of your current extension (not dropping below 400k) and personally if it was me, I would also make sure the 800k is there before you get the extension just incase something is wrong or something goes wrong.
You can come until you can't... In other words, its literally down to the discretion of the IO/supervising IO every time you try to enter even with a TRV/METV. As long as you don't have a sketchy history you should be fine but I would make sure you meet all the requirements such as 20k cash, on-wards flight etc
It depends on if they have voluntary insurance or just compulsory insurance and if they have voluntary insurance what the policies are in that insurance.
Option 2 but don't use an agent get a non-oa instead that way your money is still in the UK and you're completely legal and then meet the 65k a month every month transfer requirements for extensions.
It's minimum transfer of 65k p/m for 12 months without missing a single transfer every single month. (I'm not sure if it can be broken up into separate transfers or it needs to be 1 single transfer though).
officially no, but pretty sure they're aware since both my accounts hold Thai numbers and I've had them send me some documents out to Thailand last year. It probably helps that I still have regular income from the UK going into those banks too.
you don't ask for anything, it will ask you for your visa number which you will put Visa Exemption and the dates you are staying. It's just an automated arrival system.