how long does it take? Can the Embassy do same day processing for my China visa?

I am already in China on a tourist visa single entry. I am planning to visit Thailand for two weeks in June and return to China. So I think I will need to apply for another Chinese visa in Bangkok. Can the Embassy do same day processing? Or next day processing? Is it okay for me to leave my passport with the Chinese Embassy and then travel around Thailand without a passport? I do not really want to wait in Bangkok until my visa is ready unless is it ready the same day or the next day. Thank you.