The base model is pre-trained on 16kHz sampled speech audio from 100h Vietnamese unlabelled data in VLSP dataset. When using the model make sure that your speech input is also sampled at 16Khz. Note that this model should be fine-tuned on a downstream task, like Vietnamese Automatic Speech Recognition. Facebook's Wav2Vec2 blog Paper

See this notebook for more information on how to fine-tune the English pre-trained model.