It will work as long as your phone supports the network bands you want to use it with AND it's not locked to a carrier SIM (same thing would apply to your iPhone, it doesn't make a difference as long as the phone supports the carrier network and it's unlocked). Now, since Vietnam is usually a VERY expensive country to roam in for US carriers, you'll see a lot of on-the-go SIM card vendors right outside the arrivals gate at the airport. You can use those and they usually speak English so they can help with any questions VS purchasing around town. Also, some hotels offer a local phone with free data/local calls that you can use included with your room, so that might also be an option (not for texting, but yes for everything else).
Again, check that your phone is 'unlocked' (so it can be used with any SIM card) and here are the bands it supports for reference (assuming this is the right model you have).
https://www.gsmarena.com/samsung_gal...(usa)-6338.php
