Vietnamese SIMs are sold at convenience stores but require passport registration with a Vietnamese-only flow — fine if you've got time, frustrating after a Tan Son Nhat arrival. An eSIM skips it: you're on Grab and Google Maps the moment your phone wakes up.
- Best for
- Hanoi-Ho Chi Minh City contrast trips; Ha Long Bay and Cat Ba cruises; Mekong Delta tours from Saigon; Hoi An old-town stays; Sapa trekking from the north.
- Networks
- Roams onto Viettel, Vinaphone, and MobiFone. Viettel has the strongest signal in remote northern mountain areas (Sapa, Ha Giang) and central highlands; Vinaphone tends to be fastest in Saigon and Hanoi.
- Travel tip
- Coverage in Ha Long Bay tour boats and on the Sapa night-train route is patchy for hours — confirm your guide's pickup details and download translation packs before boarding.