you dont need an Agent, it is only less stress :) - take care : you have to wait for every legalisation about 2 days. First : Marriage ( you have to be 2-3 days before at the Marriage Hall to apply again personal) than to the Highcourt for the Stamp . Takes one day when you say you need it fast. Than do the rest.
To marry in Hkg is easy because of the requiered documents. She needs Passport and Single Paper ( Document that says that she is not married or devorced )= Cenomar. She can apply online easy. Takes about 2 weeks to get. You need your Passport and - if you devorced : the english translation from the devorce contract. The marriage is valid worldwide because of the Haager Apostile. You get a translation of this marriage certificate to Thai, than get a stamp from the Thai Consulat. Also make registration at the Phil Consulat in Hkg. All can be done in about 10 days. We used an Agency , they guide us and walk everywhere with us, - was about 33.000 Baht. So it was very easy to find everything and we had a perfect time shedule.