If your daughter is British she needs to get her UK passport, as she won't be able to get a UK visa in her Thai passport.
If a person who is a British citizen, or has the right of abode in the UK, applies for a visitor visa or for settled status to be entered into a foreign passport, the application should be refused. This is because section 1(1) of the Immigration Act 1971 confers complete exemption from UK immigration control on persons with the right of abode, subject to proof of that right. As such a person with the right of abode in the UK should not be given leave to enter or remain under the Immigration Rules. If you have a visa application from a person who you are satisfied has the right of abode in the UK, the person should be advised to apply for a certificate of entitlement instead.
https://www.gov.uk/government/publications/right-of-abode-roa/right-of-abode-roa?fbclid=IwAR1kZx7pRzRtmoCDHijtjmuF2NLEvyATgKCAJ-ebRqc3B7qLuxaGF9bqOLI