Applying for a Z type from a 3rd country

I'm a US citizen who has been in China frequently for business over the past 2 years ( I've had two business visas before, and 3 tourist types before that ). I've been offered a full-time teaching job in September, and have just submitted all the documents required to get the invitation letter, etc. If all goes well with the first bunch of paperwork, can I apply for the Z type at the Chinese Embassy in Bangkok, or by mailing my passport to an agency in Los Angeles, who would then submit it to the Chinese consulate there? I understand that the *best* way is to go back to the USA, but that will cost me over $2000. Does anyone have any *solid* knowledge or experience with this (as opposed to guesses or opinions). Thanks.