Seeking a little advice regarding an upcoming SGN connection and Visa options.

Scheduled to arrive SGN on a September Sunday evening at 7:45 PM on Thai Airways. I will have one night in SGN before departing on United's early AM flight on Monday morning (5:30AM departure). Separate tickets.

Anyone have experience or opinions with anticipated VOA wait times on Sunday evenings in September?

I am trying to decide if I should go the VOA route (easy and less $, but risk of long wait time at immigration) versus paying the extra $ and just mailing in my passport for an actual Visa.

Thanks for any insights or advice.