Viettel are the Telstra of Vietnam, and Mobiphone and Viniphone...

Viettel are the Telstra of Vietnam, and Mobiphone and Viniphone are the next two biggest.

There is some overlap in ownership too.

This article assists in explaining: telegeography

You also may be interested that Vietnam will move up the ranking the most of fastest growing economies by 2050 and will have one of he fastest growing smart phone saturation growths also.