If you okay to live like vietnamese person do yes you can live on $700 just fine. Especily if you single, healthy and love driving on motorbikes through rain and take a bit of risks.

Plus health insurance like Cigna for $100-200 unless you want to pay $10,000-20,000 in vinmec if you crash on a motorbike or get other serious sickness.

Plus border runs like $200-300 three times a year or often for cheaper depend on your paasport.

Problem that I doubt its how average SWE on HN imagine "comfortable" living.

Then if you have a partner who is not remote worker and kids there will be other surpeises for you.