Should I apply for a retirement visa to Thailand in the UK or during my 60-day visit?

Don't stuff around with "retirement" visas - just get the DTV

60 days is ample time do it here Thailand

You need get non O visa from uk ( Thai embassy ) quite easy. Then when you get to Thai you can open bank account with that. Then apply for 12 month extension ( and again each 12 months ). I had to get a letter from immigration as well ( quite easy take 4 photos with you ). When you here if you want easy way to get 12 not n extension try thaivisacentre.com on bk they are brilliant.

If you get the non o retirement in the UK, you don't need insurance or a criminal check. It should be fairly straightforward, although my recollection is that the system is a bit clunky when uploading the evidence (it might have improved)just be patient and keep trying.

Once you get the visa, come to Thailand, make sure immigration stamp you in using the non o visa.

Open a bank account in the first few days and deposit the 800,000. Make sure when you transfer the money it shows as an international transfer (if using Wise, I think you use the option to purchase a property ').

Go to your local immigration office and ask for their requirements for a 12 month extension of stay based on retirement.

Get a 6 month lease property with a contract that contains the owners id and their house ownership book.

When you get to to 15 days left of your visa, go to the immigration office with all of the evidence they requested and apply.

Keep a folder with all your documents, photocopies and photos in as you will need the same information regularly in Thailand.

Good luck and enjoy!

Non-o Evisa from London you will be required to show minimum of £18k in your current bank account as final balance on your bank statement on applying

Usually easier to get the Non O visa from London because it makes it way easier to open a bank account here. Can be done here but just easier with a non immigrant visa.