So I think I solved my 1 day overstay problem. I want to go to China for a week. Since Hong Kong is visa free for 90 days and I can visit mainland China for 10 days as long as I have an exit flight out of China, I can go to Hong Kong for a couple of days, go on to Chongqing for a few days and fly back to Chiang Mai from Chongqing on Nov 2 in time for my flight to Frankfurt. So basically I cancel the overstay issue. Is that feasible?