I am looking to setup a photography business in bangkok but I understand that this is a Thai only occupation. Does anybody know of a way I can setup up photography business or work as a freelancer and do it legally.

You can be a shareholder in such a company, but you wouldn't be able to apply for a work permit with the job description "Photographer".

Following the spirit of the law, I'm afraid that there are no "work-arounds". Following the letter of the law, you can find some "work-arounds" (exploiting technicalities, ambiguous job description such as teaching photography techniques to thai staff, etc).

You should contact Sunbelt and ask them what they think about your particular situation/project.