KR 721 then VJ 902 at Bangkok
Siem Reap → Bangkok → Hanoi
Timetable, Bangkok time
17:05KR 721 from Siem Reap at the gate
15:05VJ 902 to Hanoi leaves the gate
22 h apart on the timetable, overnight
VJ 902 leaves 22 h after KR 721 arrives on the timetable: more than half a day, so not a connection we count.