Please let us know how you get on with this and what the embassy says, if you do decide to try to use money in a Thai bank account to apply for the visa in London.
London has moved to the e-visa system and you no longer have to submit your passport or original documents to the embassy, so this may make it easier to use money in a Thai bank since you could even apply when you are in Thailand (if you were going to return to Thailand during the validity period of the visa - the risk there is that COVID rules could change to something stricter again and you waste the visa application fee).
do you mean, will they allow you to show funds in a Thai bank account when applying for the visa in the UK?
If that's the question, then I can tell you that in the past the UK embassy was amenable to this idea when issuing other visas and their only concern was making sure that the bank information was current. i.e. statements from 2 months ago wouldn't cut it.
It's almost 3 years since I discussed this with them so I don't know what the situation is now.
I suggest you contact them and ask them and if you have a way to get statements that are current, I suggest that you tell them that too at the outset to forestall any objections around the age of the age of the statements.
financial requirements for a Non-O for the purposes of retirement, from the UK embassy website:
"Financial evidence e.g. A copy of pension statement if the applicant is a pensioner, or a copy of 1-month bank statement showing your income from pension, or 3-month bank statement of at least £10,000"
However, their website is out of date so it's best to contact them to check first if you want to go this route.
Having said that, I think these have been the requirements for that visa for some years.
with the excellent advice you give and the work you have done directly with immigration to get answers and to understand procedures, it certainly felt like it was your group.
Let me just say, "Thank You", to you and the other moderators for all the work you have put into this group.
I hope that things can continue in the same way, with the same high quality advice.
If you do not enter before the 2nd of March next year...
You could go through the Non-Immigrant OA visa application process again. As things stand you will need the mandatory Thai health insurance.
Or you could get a Non-Immigrant O visa in London for the purposes of retirement (valid for 90 days) then extend it in Thailand as Robert mentioned above.
Other more complex alternatives are to enter visa exempt or with a tourist visa and then convert to a Non-Immigrant O in country then extend it. However, this may or may not be offered by your local immigration office.
Also there may be a requirement to show that the money came abroad with one or both of these conversion methods.
Using the Non-Immigrant O or visa exempt / tourist visa then convert route, you do not need the Thai health insurance. Or more accurately, you didn't need it BEFORE the pandemic began.
Now, who knows?
There may or may not be pandemic or other health insurance requirements.
What is the 'Valid Until' date on your Multiple Entry Tourist Visa?
If the borders open between Thailand and a nearby country before your original visa is no longer valid, it may be possible to do a border bounce to get another 60 days using your visa and then get a 30 day extension on top of that.
Having said that, I have no idea how immigration will look upon people who have been in Thailand continuously for many months (due to the Coronavirus) and who still try to stay longer.
is it possible for him to get 17 months of stay out of that visa by extending the final 90 days by 60 days (for visiting a family member) or is that not an option?
I agree with the others that say go to immigration and get an extension.
In the past there were no real consequences for overstaying but now there are some, such as not being able to get certain visas at at least one embassy in the region, as has already been mentioned.
Things may continue to change and you spend a lot of time in Thailand every year.
You should be able to apply for a 60-day tourist visa in Denmark. You can then extend this for an additional 30 days in Thailand if you need more time.
What is your history in Thailand?
Three months in the past six shouldn't be a problem but do you have a more extensive history in Thailand? If so, that may change things.