That is excellent. Sadly you cannot apply online for UK if abroad.
HMPO information was a shambles. After some inane emails I actually spoke to them on the phone and they told me I would not retain my passport (wrong) and that it would take at least 8 weeks(wrong). When I read out their own webpage to them about it being 4 weeks they put me on hold...then hung up.
Having said that , the VFS lady I dealt with at the UK office on Rama 9 was pretty good.
FYI - as an aside for anyone in same situation new UK passport actually just took 2 weeks from application to the notification that it had arrived (at VFS BKK)