@Yogesh ******
yeah this ain't Saigon pre-covid shit show 😮.
the fastest I've seen VFS get a brit passport back here in thailand is 8 weeks from the reports people are making.
Good luck with it, you can get the 30 day extension, then when you get your new passport I will leave it up to you to decide IF you move the stamps or just leave.
Also remember you can't use the passport you have no for international travel once you started the renewal process. What I mean is you can't bounce out and back to get a new entry stamp IF it takes more than the time you have on your current stamp plus the 30 day extension) you just run on overstay. 😕
Good luck with it (y)