First time in Vietnam: stay in North Vietnam solo or fly to Bangkok (again) for the last 5–6 days?

Hey everyone,

I’ll be traveling to Vietnam for the first time from 30 May to 26 June. I’m starting in Ho Chi Minh City and ending in Hanoi because of flight availability.
I’ll be traveling with friends from 30 May to 20 June, and after that I’m planning to spend 5–6 days solo for the first time in my life. I’ve never solo traveled before, so I’m trying to decide what to do with that final part of the trip.
Right now, I’m considering two options:
1. Stay in northern Vietnam for another 5–6 days
I’ll already have spent around 6 days in the Hanoi area with my friends, so I’m not sure if there will still be enough for me to do alone.
2. Fly to Bangkok on 20 June and stay there until my flight home on 26 June
I’ve been to Thailand several times and really love it there, especially the food, massages, and general atmosphere. The downside is that it would obviously make the trip more expensive because of the extra flight and slightly higher hotel/living costs.
I’ve also thought about Chiang Mai or Krabi again, but with only a few days and needing to fly home from Bangkok anyway, I don’t think that would be worth the extra travel. For context, I’ve already been to Phuket, some Thai islands, Bangkok, Chiang Mai, and Krabi.

My main question is:
Is there enough to do in northern Vietnam for that long, or would it make more sense to spend the last 5 days in Bangkok since I already know I love it there?
For my solo travel time, I’m mostly looking for:
• nice scenery
• street food and night markets
• massages/spas
• good food
• relaxing activities
• time alone with my thoughts
• maybe 1–2 small tours
• possibly playing pool or having a few beers with strangers
• maybe getting a tattoo, like I did in Bangkok last year since they are way cheaper than in Europe
I’m not really a big party or tourist-attraction type of person. For example, even though I really liked Bangkok, I wouldn’t be interested in places like Khao San Road.

I guess I’m wondering whether it’s worth spending the extra money to fly to Bangkok for a few days just to get that Thailand feeling at the end of the trip, especially since I love Thai food and mango sticky rice so much. On the other hand, I don’t want to leave Vietnam too early if northern Vietnam would still be interesting and enjoyable solo.
A few extra questions:
• Do you have any general recommendations for things I could do solo in northern Vietnam or the Bangkok area?
• Is it possible to find Thai food in Vietnam, especially things like pad kra pao and mango sticky rice?
• Does Vietnam have anything comparable to Thailand’s 7-Eleven availability/convenience store culture, or is that much more of a Thailand thing?
Would love to hear your thoughts, especially from people who have spent time solo in northern Vietnam or done a similar Vietnam/Thailand split.