@Dean *********
your friend needs to do exactly the steps I said in that exact order to register a marriage here in thailand
BUT
Sadly, this isn't the "how do I get married" group 😮 it's the visa advice group SO post on a group related to where you live in thailand or the britz in thailand group and ask the steps to get married.
Believe me, you're not the first foreigner here from the UK to marry a thai 😛