Do you need a return ticket to enter Vietnam — will they check at the airport?

According to available information, not having a return ticket may slow down passport control on arrival, but does not necessarily result in denial of entry. This is unconfirmed.

A flight arriving around 10am (the only plane at that time) cleared immigration in about 10 minutes. No one asked for a return ticket, and no fast-track service was needed.

Recent arrivals report that immigration officers did not ask for proof of onward travel. Buying a return ticket after arrival appears to be fine in practice.

Arriving in Nha Trang without a return ticket caused no issues. If your stay is flexible (1–2 weeks), you can buy the return ticket after arrival — it's not checked at immigration.