Originally Posted by
5khours
With a VOA, 1:35 is tight. I'd get a visa in advance in which case, 1:35 is fine. 20~30 minutes max to clear immigration, pick up bags and clear customs. Two minutes to get from arrivals to departure. Check in, immigration and security on the REP flight should take no more than 10 or 15 minutes (there is a priority line for J in security). I fly internationally out of SGN 2 or 3 times a month in J and never check in more than 60 minutes in advance.
I certainly won't say it's fine. The slightest delay from HKG and he's screwed if he has to go landside. On separate tickets and especially when a border crossing is necessary, never do that kind of connection in less than 2.5 hrs.