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

I'm Austrian and I would like to visit Hongkong for sightseeing. As I plan to travel to Hongkong with my Cambodian girlfriend from Bangkon to Hongkong, I would like to know if my gilrfriend can get her visa in Bangkok or if she has to apply in Phnom Penh.