renewing travlers visa(single)

Hi.
I am south korean curretnly traveling in yunnan. i have 90 days single travelers type and i extended by 30 days. but i wish to stay another 3 months since i would like to discover chinese minority dance/music culture which i found unique and interesting.

i would most likely not study in an intitution but travelimg around and observe the way the culture works. In this case. is it possible to renew it in the chinese embbassy in Bankok. if then what are the required documents?

lookin foward to ur kind answer. thank u so much :)