KE 852 then KE 683 at Incheon
Beijing Capital → Seoul → Chiang Mai
Timetable, Seoul time
21:55KE 852 from Beijing Capital at the gate
18:45KE 683 to Chiang Mai leaves the gate
20 h 50 apart on the timetable, overnight
KE 683 leaves 20 h 50 after KE 852 arrives on the timetable: more than half a day, so not a connection we count.