Shenzhen Visa on Arrival for Thai passport holder living in Japan

I am Thai passport holder living in Japan and planning to go to SZ for an academic conference.
I will fly from Japan to Hong Kong and then will enter SZ crossing the border.
Since I have no time to do Chinese visa application in Japan, is it possible for me to make a visa on arrival at the border?
If it is possible, how long can I stay in SZ?
Thank you in advance.