Can i apply a tourist visa here in Thailand for China?

Fara, I am afraid that the embassy might require that your resident permit for employment in Thailand is valid at least six months. This is the rule for those who apply in the third countries. If you are qualified, then you can bring your passport, filled application form, a recent passport photo, round-trip air tickets, hotel reservation and your resident permit for employment (original and copy versions) to apply for a L type.

Thanks for your reply. Yes, i still had my work permit valid for more than 6 months in thailand. And do i need an invitation letter from china or it doesn't matter?

It doesn't matter. If you have hotel reservations and round-way tickets, you don't need to submit the invitation letter.