12 month multi-entry F Visa

Hi, I am an American considering volunteering to do market research for a foreign friend's WOFE company in China for the next 8-12 months. Reason for writing is I would like to know if it is possible to get a 12-month multi-entry F Visa from the Chinese Embassy in Bangkok. If so, are there any 60 or 90 day exit restrictions? And what documentation is required other than the appropriate visa forms and an invitation letter from the company that will be inviting me to do the research in China? Thanks for any information you can offer me about the situation on these visas through the Chinese Embassy in Bangkok.