Thank you for contacting www.vietnamvisa-easy.com,
In your case, your flight are on the two different airlines and 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. You are required a visa for Vietnam this time eventhough you are not enter the country or even leaving the airport. Thus, we recommend you to apply for multiple entry Vietnam visa.
We do hope the information is clear and helpful for you.