I done a British passport for my Thai daughter last year its a piece of cake to do mate Honestly They just need all the mothers papers translated into English which my partner got done in Khon kean for a few hundred baht then a colour original copy of my paperwork we then posted them to Bangkok I had to travel back to the UK a few weeks later got an Email from passport office in Liverpool saying they have issued my Daughter a passport and would be Available to collect in Bangkok i then had to Email the passport office in Bangkok to organise a time an date to collect in person i definitely paid less than £200 for the whole shebang thats with travelling to Bangkok from pattays to collect in person . Good Luck mate ..