Are there nonstop flights from Siem Reap (SAI) to Luang Phabang (LPQ)?

Yes. Vietnam Airlines fly this route. Flight time is about 1h 24m.

What is the fastest connection from Siem Reap (SAI) to Luang Phabang (LPQ)?

via Pakse ≈ 2h 4m, via Bangkok ≈ 2h 16m, via Bangkok ≈ 2h 17m (estimated flying time, excluding layovers).

from 12,000 JAL miles (economy, one way, based on the published award charts).

Siem Reap-Angkor International Airport (SAI) to Luang Phabang International Airport (LPQ)・759 km

Nonstop flights available (1 airline). Flight time about 1h 24m. Nonstop return flights also operate.

With milesJAL 12,000 miles+ (via BKK)Economy, one way, estimate. Tap a connection for miles by cabin.

5 one-stop options, sorted by estimated flying time. Tap one to see the airlines on each leg and booking links.

Times are estimated from distance. Check schedules, frequency and availability with the airline or a booking site.