I have a police report and I believe I have to make an appointment at the UK embassy in Bangkok to apply for a renewal, but my question is what about my visa and retirement extension, which I renewed yesterday?

All you will get at the UK Embassy is an Emergency Travel Document.

To obtain a new passport open the link for detail

https://www.gov.uk/government/world-location-news/changes-to-british-passport-services-in-thailand--2

Once you have a new passport a visit to the immigration office where the extension was obtained will enable its reinstatement.

When you get your new passport they will reinstate your extension of stay stamp and if they have the info do a stamp with info about the visa your used for entry to the country. Do you copies of your visa and extension stamp and your TM6 departure card?

Info on reporting your lost passport and link for applying a new one here; https://www.gov.uk/report-a-lost-or-stolen-passport/y/abroad/thailand

Hi Joe, I have a copy of the main page of my passport but nothing else. Samui immigration has copies of every page as the guy was in a real bad mood on Thursday and sent me away to copy every single page having given him the main pages.

They might pull your file to get the visa info. The extension they can get from their data base.

I'll give immigration a call on Monday. In the meantime I'll get the stolen passport form filled in. Thanks for your help.