I am a Norwegian citizen working in Thailand .

I have a Thai work permit and need to make regular business visits to China. Since early 2011, I can no longer obtain a multi-entry visa to China from the Chinese embassy in Bangkok - even with company invitation letter from our Shanghai office. Company colleagues living in Malaysia obtained 2 years multi-entry to China with the same invitation letter.
Can you please advice what I need to do to obtain multi-entry as I visit China almost every 2 months