OJAS

If I were you I would be far more concerned about the OP's initial use of incorrect terminology through referring to a "Non-Immigrant O (Retirement Visa)" for his dad, bearing in mind that, in the case of retirement, immigration offices issue fresh non-O visas (based on conversions of recent entries into Thailand) as well as fresh annual extensions of stay.

Unless the OP is American, Australian or British (and his references to Europe and the EUR currency would appear to indicate that he is none of these 3 nationalities), he might be able to obtain a suitable income confirmation letter/affidavit from his home country embassy in Bangkok in lieu of making physical monthly transfers. EDIT: But that said, however, his clear preference is to go down the 800k/400k route instead.

In that case I would strongly recommend that you allow at least 15-20 minutes to get from your car to the VFS office should you decide to renew in person. Quite apart from your physical limitations (which don't sound all that dissimilar to mine), you might well find yourself having to endure a lengthy wait for the lift to convey you from the 5th to 8th floors, if my experiences a few months ago were typical!

While the postal method may well be available for those whose home countries offer reasonably easy and graceful passport renewal services to its expat nationals living in LOS (as in the USA's case for instance), it is, unfortunately, a complete no-no as far as we Brits are concerned. Instead we are required to make physical trips in person, regardless of our state of health (or have agents undertake these trips on our behalf) to offices in Bangkok or Chiang Mai in order to (1) deliver our renewal applications, and (2) collect our replacement passports several weeks later. Don't ask me why snail mail postal methods dating back around 200 years are considered far too hi-tech by those clowns in His Majesty's Passport Office back in the UK who are responsible for the cumbersomely bureaucratic passport renewal procedures which have been inflicted on us Brits living in LOS!

I can definitely confirm on the basis of personal experience (from when I subjected myself to the dreaded With-It Tower Passport Renewal Experience 6 months ago) that parking for VFS customers is available on the 5th Floor of With-It Tower. It is, however, then a bit of a walk to the lift which will convey you to the VFS office on the 8th Floor, followed by a further bit of a walk to said office. Please note, however, that there are absolutely no loos that you will encounter between the car park and the VFS office (or at least none that I could locate despite encouraging notices to the contrary). And there are no loos in the VFS office itself. In addition, if you arrive for your appointment early, you'll need to stew in your car since the miserable bozos in charge of the car park won't allow you to keep your car's engine running to power its aircon. Finally, please hang on to the ticket which will be issued when you enter the car park, and take it to the VFS Office with you to get it stamped so as to secure a not insignificant reduction in the parking charge when you eventually leave. I missed out on doing this for the first trip!

Yep, I was also moaned at in no uncertain terms for the lack of monthly transactions at Rayong on 20 July. As a result I've now set up token 20 THB transfers (which, thankfully, don't attract any supplementary bank charges these days) into my dedicated Krungsri account on 20 August, 20 September and 20 October to cover the 3-month post-application 800k seasoning requirement. In due course I'll be setting up token transfers for November, January, February, March, April and May (these shouldn't be needed for December or June, though, since these are the months when Krungsri makes interest payments into my dedicated account). @Eff1n2ret - to be aware of this further Rayong requirement (which unfortunately I forgot to mention previously).

Very few of whom are to be found sat behind windows at immigration offices, though, unfortunately.☹️

But unfortunately almost certainly not for an equally - if not considerably more - dim-witted check-in assistant at LHR who will almost certainly derive considerable pleasure from gleefully denying him permission to board his outbound flight to BKK solely on account of the spelling inconsistencies!

As already said, perfectly possible to switch from retirement to marriage as the reason for annual extensions of stay. It should, however, be noted that, in the year in which the switch is made, the new marriage extension will be dated from when it is applied for rather than from when the permission to stay granted under the previous retirement extension expires.

Sounds fishy to me.

You can actually apply for a new extension of stay up to 30 days before your current permission to stay expires at most offices - and even up to 45 days beforehand at some (e.g. Chaengwattana and Chiang Mai). And retirement extensions are normally processed and issued on the spot at most offices, with no need to leave your passport with them overnight (Jomtien are the notable exception in that regard, though).

I was never required to have my British Embassy income confirmation letters notarised in this way.

Agreed - use it or lose it as the old adage goes!

For the future you might instead wish to consider obtaining consecutive 6-month statements (which Bangkok Bank branches can issue on the spot) at 6-monthly intervals. That's certainly something I did when using the 65,000 THB monthly income method for my retirement extensions based on my Bangkok Bank account, with no adverse reaction from Immigration.

Assuming that your wife is Thai, are you really that skint that you can't even afford a legitimate marriage extension?

It strikes me that, in the case of those of us who have already lived in Thailand for several years, a Thai criminal records check would be more appropriate. But, since immigration offices are part of the Royal Thai Police, one would like to think that they would have ready access to Thai criminal records pertaining to recalcitrant foreign retirees in any event. That said, though, this is, of course, Thailand, lest we forget..........

So how would this work in the case of those who, like myself, haven't lived in their home countries for 15 years?

So presumably all you have needed thusfar to provide in support of your retirement extension applications at Khonkaen have been an account confirmation letter from your bank plus copies of relevant passbook pages? If so, I suspect that what Khonkaen are now requiring for the first time in the case of retirement extension applications based on 400k/800k in the bank are, in fact, 12-month statements, regardless of what the officer told you. In connection with the post from @DrPhibes, 2-month statements would only make sense in the context of marriage extensions (as in his case) which are subject to different financial requirements from retirement extensions. Maybe the officer who spoke to you was labouring under the mistaken belief that you are, in fact, staying in Thailand on the basis of marriage, rather than retirement, extensions?? (Either that or he was talking through his derriere). If Khonkaen are now insisting on 12-month bank statements in support of retirement extension applications based on 400k/800k in the bank for the first time, they seem not to be the first office to have started insisting on this additional requirement in recent times (over and above those offices which have insisted on it all along). For instance, it has been reported on here by @DrJack54 that Chaengwattana (Bangkok) have now introduced this additional requirement. And I personally had it sprung on me as an unpleasant surprise when I applied for my latest retirement extension at Rayong a few weeks ago. Makes me seriously wonder whether some general directive has recently been issued to immigration offices on this requirement by Immigration Bureau bigwigs? When it comes to obtaining 12-month bank statements, it should be noted that Bangkok Bank branches require at least a week's notice to obtain these from Head Office in Bangkok. All other banks should, however, be able to issue these statements on the spot over the counter.

Do you use the 400k/800k bank balance or 65k monthly income method?

Not just a new requirement at CW but also one at my local office (Rayong) as I found out a few weeks ago: https://aseannow.com/topic/1301303-new-rayong-immigration-requirement-for-retirement-extensions-based-on-800k-in-the-bank/ Makes me seriously wonder whether those offices who haven't hitherto insisted on 12-month bank statements in the case of retirement extension applications based on 800k in the bank have now been ordered by Immigration Bureau top brass to fall into line with those who do?

Already done in the case of those whose original visas are of the non-OA and non-OX varieties. But the requirement for criminal records checks would need to be extended to those seeking non-O visas for retirement - which might, of course, require some thinking on Pol Gen Surachate's part outside the "retirement extension" box!

But in the context of retirement extensions would it not be more likely that we would need to apply for a Royal Thai Police certificate (https://www.royalthaipolice.go.th/downloads/clearance.pdf) rather than obtain clearance from our home countries? And where would we be able to submit our applications for these certificates? At our local cop shop? Or would a physical trip to RTP HQ in Bangkok be needed (every year presumably)?

There certainly used to be an alternative to the Government Gateway known as GOV.UK Verify - which did require a UK address to be input as I found out when I tried unsuccessfully to register for this facility from Thailand a couple of years ago. However, as will be evident from the link below, it is no more:- https://www.gov.uk/government/publications/introducing-govuk-verify/introducing-govuk-verify But if, indeed, new Government Gateway accounts can now only be opened with a UK address, this is tantamount to barking madness of the highest order IMHO. What about those who, like myself, no longer have access to a UK address for whatever reason? The UK government certainly does appear to be excelling itself in seemingly being firmly joined-up in at least one particular respect - namely in making life as difficult as is humanly possible for us expat retirees here in LOS (where it is, of course, being eagerly aided and abetted by its Thai counterpart). We already have HMPO and DWP to "thank" for the cumbersomely bureaucratic procedures which have been inflicted on us over the past 10 years or so in the areas of passport renewal and State Pension life certificates respectively. And now HMRC seem intent on joining the "party" by preventing expats from opening new Government Gateway accounts, if your latest unsuccessful attempts are now the new norm.

No dickey-bird mention in the following link of any need for a UK address in setting up a Government Gateway account, unless I'm missing something:- https://www.gov.uk/government/publications/access-our-services-using-government-gateway/use-a-government-gateway-account

Unfortunately, the sad reality these days is that the concept of "joined-up government", as so enthusiatically espoused by the likes of Tony Blair and John Prescott 20 years or so ago, is now completely dead in the water, with individual component parts of The Great UK Government Machine in all probability now acting under strict orders emanating from On High to confine their activities to matters which fall strictly within their purview, with blinkers firmly attached to prevent any "undesirable" sideways glances into areas for which they are not responsible.