Are there nonstop flights from Changsha (CSX) to Hanoi (HAN)?

Yes. China Southern Airlines fly this route. Flight time is about 1h 46m.

What is the fastest connection from Changsha (CSX) to Hanoi (HAN)?

via Nanning ≈ 2h 17m, via Guangzhou ≈ 2h 35m, via Shenzhen ≈ 2h 43m (estimated flying time, excluding layovers).

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

Changsha Huanghua International Airport (CSX) to Noi Bai International Airport (HAN)・1,077 km

Nonstop flights available (1 airline). Flight time about 1h 46m. Nonstop return flights also operate.

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

16 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.