Briefly - I left UK mid-March with 90 day visa. Subsequently extended to one year multi-entry but my UK passport expires 1st June 2026. I need to return 'home' in the not too distant and think it unlikely I will be able to return this year. 6 months unexpired passport is required to enter LOS. 

For what it's worth I booked an appointment with VFS in BKK to explore the possibility of getting a new passport, then local immigtation office (small town and reasonably chilled) to move visa to new passport.

Smart, stupid, other suggestions?

8 minutes ago, Seagull Sam said:

Subsequently extended to one year multi-entry but my UK passport expires 1st June 2026.

You did not obtain a "one year multi entry" 

You obtained a 12 month extension + a multiple reentry permit. 

11 minutes ago, Seagull Sam said:

 6 months unexpired passport is required to enter LOS

Thats note quite correct. 

With a reentry permit thai immigration would not have issue with the 6 months you refer to. 

Airlines can be unaware of this. 

13 minutes ago, Seagull Sam said:

For what it's worth I booked an appointment with VFS in BKK to explore the possibility of getting a new passport, then local immigtation office (small town and reasonably chilled) to move visa to new passport.

Thats best plan. 

They won't move the visa but make notation in new pp. 

Simple process. You will need attend immigration office. 

Where did you obtain the reentry permit? 

 

When you go "home" get a new passport.  You will keep your old one and the extension/re-entry will still be valid on your return.  It will be far easier/cheaper to renew your passport in the UK than doing it through VFS.

Plan B (assuming that you have a re-entry permit when you refer to 'multiple entry'):-

 

Just renew your passport in the UK, you will be there long enough. Then you just need to carry both passports - one, the new one, the second the old one with the extension/reentry permit in.

 

Get the details transferred to your new passport when you get back.

24 minutes ago, DrJack54 said:

Thats best plan. 

They won't move the visa but make notation in new pp. 

Simple process. You will need attend immigration office. 

Where did you obtain the reentry permit? 

Thanks to all and in and in answer to Dr Jack, there's nothing to be lost by seeing what they say at VFS. If it can be done reasonably quickly they will remember me and gf at immigration.

Phetchabun BTW, relatively new office and very few farangs in this part of the world.

19 minutes ago, Seagull Sam said:

Thanks to all and in and in answer to Dr Jack, there's nothing to be lost by seeing what they say at VFS.

By all means... however read your OP too quickly. 

Seems you will be in UK for a period much longer than needed to apply for new pp. 

Good advice from others above. 

Renew in UK. 

Travel with both passports. 

Make sure to show both to immigration on arrival upon return. 

 

Appreciated and understood.

I'm not in a big hurry to return so to have both passports before departure would make make me feel more comfortable. 

Otherwise new passport from UK would likely be fine. The Thai government are constantly moving the goalposts and there's always the possibilty of a jobsworth on my return to LOS.

hotandsticky's Plans A&B suggests both approaches might work.