Upvote:0
As stated in Timatic, the database used by airlines:
Passport exemptions: Passengers with a Permanent Resident/Resident Alien Card (Form I-551).
For Vietnamese border control:
Passport Exemptions: - Nationals of Viet Nam residing in the USA with a Certificate of Visa Exemption together with: a US Permanent Resident Card (Form I-551)
So if you can get a Certificate of Visa exemption (required to exit Vietnam), then you do not need a passport to to travel, only a Green card, although some US officials have been known to require a passport. If they (incorrectly) tell you you cannot re-enter the US without one, ask for their supervisor.
Upvote:3
The US will allow you to re-enter with only your green card, unless you have lost your permanent residence status (more below). Vietnam may require you to have a passport before you leave, however, as will the countries through which you are transiting, if any. You should probably get a passport before you leave.
Whether you need to replace the US visa before you return depends on what kind of visa it was.
More precisely, whether you need a visa to enter the US depends on the rules for the loss of permanent residence:
Abandoning Permanent Resident Status
You may also lose your permanent resident status by intentionally abandoning it. You may be found to have abandoned your status if you:
- Move to another country, intending to live there permanently.
- Remain outside of the United States for an extended period of time, unless you intended this to be a temporary absence, as shown by:
- The reason for your trip;
- How long you intended to be absent from the United States;
- Any other circumstances of your absence; and
- Any events that may have prolonged your absence.
- Note: Obtaining a re-entry permit from USCIS before you leave, or a returning resident visa (SB-1) from a U.S. consulate while abroad, may assist you in showing that you intended only a temporary absence.
- Fail to file income tax returns while living outside of the United States for any period.
- Declare yourself a βnonimmigrantβ on your U.S. tax returns.
If you have abandoned your permanent resident status, you cannot use your green card to enter the US. In that case, you will need a visa.
If you have been outside the US for more than a year, you will need a new immigrant visa, called a returning resident visa.