In case you have missed this info in the Bangkok English language press.. Starting on March 08, the British Embassy in Bangkok will no longer issue passports locally. They will now be processed in Hong Kong. Details are at www.ukinthailand.fco.gov.uk
Appears to be in line with an email my mate sent me about British Passport renewals in Indonesia also. The email also said that the cost of the courier services would be included in the renewal fees.
Fortunately i just got mine renewed in Singapore so it should do me another 3/4 years before i need a new 48 pager.
If it's like the Indonesian circular i read, Yes you will still apply in Bangkok, but the passport will be couriered to/from Hong Kong for renewal within the time allowed.