Honestly if you're American spend a few more months saving up a lot and you'll be able to spend much more time here.
Try and get some online freelance work or freelance locally as well for extra cash. Make it a 3 month goal, with $5k you can be comfortable for a bit then think of your next move.
For vietnam since i dont have a Vietnamese passport they offer a 6 month visa exemption booklet instead. (same as those who marry a Vietnamese national)