A small town with thick walls

Hoi An is not a coverage emergency. It is a low-rise town a short ride from Da Nang, and Viettel covers the approach, the Cam Nam side, and the streets visitors actually walk. The annoyance is architectural. Shop-houses are deep, wooden, and sometimes lined with metal roofs. A QR payment that fails at the back counter and works on the doorstep is a radio shadow. Reinstalling the eSIM does nothing useful there.

An Bang and the other beach villages are a few kilometers toward the sea. You get a coastal signal: good enough for maps, a weather check, and uploading a few photos, not a promise of the 5G download number from a national report. If you are working, do the video call from the town side or from Da Nang, where the grid is denser, or stay inside the 5GB consciously. Hotspot works. It is the same bucket.

The ride from Da Nang

The coastal road and the inland route are both used by Grab and by private cars. They are not mountain roads. Signal along them is the normal central-coast pattern, with a dull patch here and there rather than a long blackout. If you are continuing north another day, the interesting gap is Hai Van, described on the Da Nang page, not the Hoi An shuttle.

Spend the data on translation, maps, and photos you actually send. Automatic camera backup to a cloud service will eat a beach afternoon without you noticing. Turn that off on mobile data if 5GB is the plan for the whole day. The counter resets at 23:59 Vietnam time, which is late enough that a dinner outage is annoying and early enough that the next morning is a fresh 5GB.