U.S. citizens must obtain a tourist visa to enter Vietnam. The visitor’s passport must have at least six months validity past date of arrival. Visas can be obtained in person or by mail from Vietnamese Embassies in the United States up to six months prior to travel. Visas are usually valid for only one entry, but multiple-entry visas can be requested. Without these documents, you will be immediately deported. Vietnam takes immigration very seriously and use of fraudulent documents could result in criminal prosecution and imprisonment.
It is possible to live in Vietnam as a retiree, but Vietnam does not offer an official retirement visa. However, it is legal for a foreigner to remain in Vietnam indefinitely with a tourist visa. It’s simply a matter of extending your visa through either a travel agent or directly through the immigration department, and extensions are easily granted.
Eventually, you will have to leave the country, but you can return as soon as the next day. Perhaps you’ll be able to stay 18 months before having to make a border run… perhaps longer. This is not illegal; it’s a realistic option for the retiree who would like to stay in this country indefinitely.
Residency in Vietnam can lead to naturalization in this country, but there are several requirements, including renunciation of prior citizenship, adequate knowledge of the Vietnamese language, and five years of residency.