We are just preparing our application again. Pin now has the following papers in Thai language

Land deeds

Papers about her family from Amphur

Birth certificate

Paper from Amphur guaranteeing that she is not married

Letter of reference from Police to say no criminal history

Are these papers that the embassy will need translating or do they see tham so regularly that it will not be neccessary?

I know that maybe this may seem like overkill but I do not want to leave anything to chance.

Sorry I do not know the exact names and details of these papers either

I would argue that there's no absolute need to have them translated because, as you say, the embassy has Thai staff who can be asked to read them. However, for presentational purposes, it wouldn't harm to have them all done.

Scouse.

Nice one for the info Scouser. Is nice to know it is not neccessary to translate but it may add the icing on the cake for presentation purposes.

I would suggest getting them translated anyway. Anything that makes the ECO's job easier!

See also 8.9 - Supporting documents.

You should normally insist on seeing the originals of supporting documents as alterations to a document are not always apparent on a photocopy. This is particularly important in documents relating to birth, death, marriage, civil partnership or divorce.

Original documents should always be returned to the applicant. Take particular care not to damage or destroy originals if they have been left by the applicant.

Translations

In the event of an appeal against a refusal, translations of supporting documents in a foreign language will need to be sent to the Appellate Authority. Where translation services are not available at Post, you should ensure that applicants provide certified translations of all relevant documents. The text of the translations must be clearly laid out so that the originator, addressee, date and signature are readily evident.

See also 8.9 - Supporting documents.

Thanks for the link Vinny, surprisingly have never read these details before. Now I have a better understanding of the ECO's guidelines.