Int'l flights to/from SGN (Tan Son Nhat International Airport) a/k/a Ho Chi Minh City lands at/depart from Terminal 1. Domestic flights use T2, which is to the right of T1. As you exit from T1's arrival gate, (a short walk then go downstairs follow signage/arrows - after clearing immigration, claiming luggage & going thru customs) It's a relatively small terminal & at the early morning hours, unlikely to be very busy. If everything is on schedule & flying C - you should be finished with everything in 30 to 45 minutes, go outside into the fresh morning air, turn right & proceed to T2 which you will see directly ahead of you.
If there are no bag drops, just use the (free, as I recall) luggage cart to roll your bags - then, find your connecting airline's check-in counter & get your BP (?) unless it's already issued. No "Sky Train" or underground walkway, etc. between T1 and T2 - it's all outdoors. A total of 95 minutes is on the tight side but manageable, skip the bathroom stops will save you a few minutes. Check with AF and VN about their interline arrangements about ticketing & luggage transfer, bag drops, etc. Regardless, you will need to go through security again at T2 with your BP & ID's in hand, etc.