Vietnam Airlines from Siem Reap to Luang Prabang has 1 flight every day. And there are 17 flights per week flying out of Siem Reap which connect to Luang Prabang.
The price for economy class – one way ticket of Vietnam Airlines from Siem Reap to Luang Prabang is 6.722.000 VND (or ~$334 USD)