The IRS standard mileage rate as of January 1, 2022 is 58.5¢ per mile driven for business, so your
approximate mileage reimbursement for this trip would be
$243.95 (this is for a one-way trip,
double it if you're calculating round trip).
This depends on the flight distance from Pakse to Vientiane which is 289 miles. Most airlines have frequent flyer
programs and they usually measure by flight distance, so the flight
time is just for your reference if you're planning a trip.