Change Surname Of Thai Daughter To Mine Without Marrying

[azAZ09]

I need to get my illegitimate daughter a UK passport in my family name. The UK embassy advise they will only give a passport in the same name as is on the birth certificate.

She has a Thai birth certificate on which I am named as father but she has her Mother's family name

Can anybody advise the process for legally changing her surname to my surname, before I apply for a UK passport? The mother is a willing participant to this change

When we registered the birth at the local amphur, we were told we had to be married for my daughter to take my surname. As they wouldn't accept my name then, do we need to apply for a legal name change at the same amphur, or can it be done at any amphur, or perhaps court, eg in BKK? If it has to be at the same amphur, I'd be confused as to why it couldn't have been done at the time, so I'm suspecting it has to be some form of court petition instead.

On a related subject, are there only certain official translators who are recognized by the embassy as authorized to translate the birth certificate? If so, are they listed somewhere?

Look forward to any advise to this rather urgent need, and sorry if the subject has been posted before, but I couldn't find it if so.

Appreciate your help

[think_too_mut]

When we registered the birth at the local amphur, we were told we had to be married for my daughter to take my surname.

How could that be true?

My daughter was born before I married her mother and the girl bears my surname.