What is the best visa option for a 66-year-old retiree planning to split time between Thailand and the UK?

The standard 60 day tourist visa would do the job with one extension and one hop out/in and one more extension Simon.

I am doing the same ,came on a 60 day multiple entry that last 6 months so every 60 days you have to leave and returned and get 60 days each time, this can be done right upto the last day of your multiple entry visa that lasts 6 monthes then you will get another 60 days so you can get at least 6 months easily, even more, it costs £150 on line from Thai embassy in London.

This may look like the best option but buy the time you have paid £150 plus a boarder run every 60 day costing more money and being a pain ,I decided to get a 1 year retirement visa which was sorted by an agent quickly and simply,you don't need to have the 800,000bht in the bank the agent sorted that for me,in the long term it cost less and a lot less hassle .

If you want to know anymore detail Message me.

My retirement visa has to be renewed each year but the agent sorts it all out for bht

I've been using the METV for several years running, (typically for 5 month stays). It allows for 180 days with two mandatory exits after 60 days. If you actually plan a 6 month stay and take two exits to neighboring countries there'll be no issue with staying under the 180 day threshold if that's a concern.

Thailand has concluded 61 double tax agreements with countries worldwide.

Same boat as you. If the 60 day free exemption continues I'll do that, if not I will apply for a non immigrant o visa pensioner. That will get me 90 days. Then I will have 2 options, go down the route of a 12 month extension with the appropriate funds or go to neighbouring country for a holiday and return for 30 visa exempt then extend that for a further 30 days. 5 months will do me. I like the first option better if it lasts.

I believe HMRC UK residential status for taxation purposes requires minimum of 183 days in the UK during any tax year period. Does not have to be continuous. Also, don't forget, UK tax year runs 6 April to 5 April. Thailand use the calendar year, so 1st Jan to 31 Dec. You may wish to plan accordingly.

180 days in Thailand no issue. I can guide you.

I would ensure that you spend 181 days in the UK to remain a resident and ensure your pension is not frozen and a maximum of 179 days in Thailand to ensure you are not tax resident in Thailand. 6 month Multiple entry visa is your friend

My friend does same but uses multi entry tourist visa. But i think with new 60 day visa expemtion it makes that kind of pointless at moment. 60 + 30 Border run then 60 + 30.

You can plan border run somewhere nice if you havent visited other parts of S.E.Asia and get cheap flights from air asia way in advance.

If you don't want to be tax resident in Thailand keep your stays to under 180 days per annum

You could do all this without any visa. Enter visa exempt and extend then exit and re-enter visa exempt and extend again. 180 days in Thailand no issue.