Just a quick update !
My UK Passport was full.
I applied for a New Passport in Bangkok and was told it would be about 4 weeks.
I collected my New Passport Today.
It took only 14 Days.
Great service and very pleasant and helpful staff.
TLDR : Answer Summary
An expat shared their experience about renewing their UK passport in Bangkok, stating that the process took only 14 days instead of the expected 4 weeks. They praised the pleasant and helpful staff at the consulate.