Replacement Thai marriage certificate

Hello all
I'm posting for my friend, he recently married in Chiangmai to his Indonesian wife (myself also) but they have lost the documents from the marriage, all was done correctly at own embassy etc and registered at the Indonesian Embassay in Bangkok after the marriage, but the documents have just disappeared
Would anyone know how to go about replacing these and typical cost
Thanks in advance

First obtain copies of marriage certificate from district Amphur office where registration of marriage took place.  You then follow the same procedure as before.

Many thanks, what documents would they need as in this case at Chiangmai she is Indonesian he is from United Kingdom, would passports and ID be fine? Also would they need an appointment or could the husband or wife just turn up etc? Again many thanks

Appointment should not be required and take passport as identification.  If something else is required there will let you know.