Sockets & plugs
Vietnam uses 220V, 50Hz with sockets and plugs Type A, Type C and Type D.
Type A
Type C
Type D
Adapters and transformers
No adapter or transformer needed
Sockets & plugs
All sockets/plugs in Vietnam are the same as in Philippines so there is no need for an adapter.
Frequency
Frequency difference (60 Hz in Philippines vs 50 Hz in Vietnam) is generally not a problem - almost all items (except some types of clocks) will work on both and you shouldn't worry about it.
Voltage
Vietnam also uses 220V as Philippines so you don't need a converter/transformer to convert a voltage as it's the same.