My wife only changed her name after we registered our marriage. However, many Thai people change their names (sometimes more than once) for other reasons than marriage (for luck, for fun, for whatever reason) and if they're then going to get married, they would need to bring that paperwork with them so that their current documentation (ID card, House Book etc.) will all match up with the Amphur office details they have on them. It's during this process that the officials determine that the person is free to marry (not currently married) and why we, as foreigners, need to provide the Affirmation of Freedom to Marry documentation from our embassy because, unlike the Thai person, we are not in their system.
The marriage certificate details the names of the people marrying, and will have your fiance's maiden name on it. It is after that process, if you both decide she will change her name to yours, that the name change takes place. That is the part that would need to be done at the Amphur office she is registered with which is why I suggested the trip back there after you marry. Obviously if you decide to marry at her local Amphur office, then both can be done at the same time. It doesn't take long, it's just a form, a couple of signatures and a new ID card.
"You're so unapproachable!"
"And yet, here you are."
I read it had changed too, as of 29th March 2019 there is no mention of Sheffield and a fee of £75 has now been added
"All supporting documents can be submitted by your sponsor or an agent at any of the following locations in the UK
- London: 66 Wilson Street, London, EC2A 2BT
- Birmingham: 5 -14 South Road, Smethwick, Birmingham, B67 7BN
- Belfast: Merrion Business Centre, First Floor 58, Howard Street, Belfast, BT1 6PJ
- Leicester: C/O Peepul's Centre, Orchardson Avenue, Leicester, L E4 6DP
- Cardiff: Temple Court – 13A Cathedral Road, Cardiff CF11 9H
- Manchester: 50 Devonshire Street North, Manchester, M12 6JH
- Edinburgh: 1 Rennie’s Isle, Leith, Edinburgh, EH6 6QT
- Liverpool: SUITE NO 207,Second Floor, Graeme House, Derby Square, Liverpool, L2 7ZH
- Bradford: Skipton Chamber 16-18 North Parade, Bradford, BD13HT