Can Cambodian people apply for Hongkong Visa (for sightseeing) also in Bangkok?

I'm European and I would like to visit Hongkong for sightseeing with my Cambodian girlfriend. As I will meet her in Bangkok we plan to start our trip to Hongkong in Bangkok. I would like to know if it is possible for my girlfriend to apply for Hongkonk visa in Bangkok and if so what documents she will need.