Your embassy should have a list of accepted translation offices on their website, plus a list of what to do in your language and in Thai.

Took us 3 days in Bangkok without any crazy extra costs of angencies - including prenup at Siam-legal (you sure want one and it must be before marriage!!).

Get the list, get the docs mentioned in the list.

Prepare the prenup via mail.

Took us about 2 weeks (switzerland is fast, germany would be about 3 months).

Choose the translation service you like. They will also do the run to the ministry for small money.

Be very early in Bangrak, they allow limited number of people!