Begin with the receiving authority
There is no universal instruction to translate every Thai document. Requirements depend on the German authority and purpose: civil status, family reunification, employment recognition and school enrolment each have different rules.
Create an inventory with four columns: document, intended use, receiving authority and stated form requirement. Then confirm whether the authority wants the original, a certified copy, a German translation, legalisation or another form of authentication.
Protect the chain of documents
Use translators accepted for the intended procedure. Keep Thai originals separate from everyday appointment copies, and carry them in hand luggage during the move. Scan secure reference copies for your own recovery needs, but do not email identity documents casually.
Names and transliterations deserve a deliberate check. If spellings differ across passport, certificate and translation, raise the issue before an appointment rather than asking a clerk to reconcile it on the spot.