Thank you for contacting www.vietnamvisa-easy.com,
In your case, your flight are on the two different airlines, if they are partnering with each other, your luggage will be transferred from the first to the second one, you do not need to go through the immigration or customs. That means techically you are not entering the country, no visa is required.
In case they are not partner airlines, you will have to go through immigration or customs to collect and re-check your luggage no matter where you are going on your second airline. If it is the case, you are required a visa for Vietnam eventhough you are not enter the country or even leaving the airport.
If you are not sure, please double check again with both of your airlines.
We hope the information is clear and helpful for you.