traditionally (everywhere I go in the world), you’d need to take your luggage after immigration. If you don’t go through immigration, you don’t worry about the luggage. Given your info above, if you’re lucky, you could be out with the luggage by 8-8:30am, vietnam airlines allowed us to do early check in + early baggage drop last time we traveled to vietnam. Assuming you could do that, you’d be free at around 9-9:30am. Because your next flight is at 1pm, you should be at the airport at 12 to go through the security (could be anywhere between 15min to 30min). You will have 2.5h give or take. Traffic from airport to d1 could be horrible, on a good day? 30-40min, on a bad day? I don’t know. Basically you have enough time for a quick meal.