The visa exemption certificate can have a maximum validity of 5 years, while it must expire at least six months before the passport or travel document to which it is attached.
When there are more than six months of validity left, the holder can generally receive a residence permit of up to 180 days per entry.
An extension may be considered when there is a guarantor and a valid reason.
For a Việt Kiều, this is therefore a particularly interesting option to consider before multiplying e-visas.