How to get the multiple entry visa for Thai Citizen as we sourcing for fabric and garment in China?

If you have never been to China before, it's impossible for you to apply for a multiple entry China visa. Do you have partners in China?

We are sourcing agent in Thailand. We are currently travel to China for sourcing and buying garment & fabric for many years. We travel to China many times a year. Sometime we suddenly travel for inspection the goods. Our trip is between 7-10 days each time. Please kindly inform what is the actually place that our vendors/factories have to submit the document to sign or issue letter for permitting 1 year multiple entry visa.

I think you may just apply for a single entry visa to China for the first time. After you go to China more than twice, you may be granted a multiple entry China visa. Anyway, you can contact the China Embassy directly to get exact info. about this.