Invitation letter: 6 months, Visa only 1 month!

Hello, I have an invitation letter from a Chinese company to visit China for 6 months. I would like to apply for a multiple-entry "M" type in SE Asia or East Asia: what embassy offers such an entry permit to EU citizens?
(Remark: I tried the China embassy in Bangkok, but they only give out single-entry 1-month entry permits to everyone, no matter what documents provided.)