Per the Immigration and Nationality Act (INA), you may lose your permanent resident status (green card) if you commit an act that makes you removable from the US. If you commit such an act, you will have to face an immigration court to establish your right to remain as a permanent resident.
Abandoning Permanent Resident Status :
You will be considered to have abandoned your permanent resident status if you:
shift to another country intending to live there permanently
remain outside of the US for more than a year without getting a reentry permit or returning resident visa. However, in determining whether your status has been abandoned, any length of absence from the US may be considered, even if less than a year
remain outside of the US for more than two years after issuance of a reentry permit without obtaining a returning resident visa.
Did not file income tax returns while living outside of the US for any period of time
declare yourself a “non immigrant” on your tax returns
How to Apply To Renew a Green Card
If you are a permanent resident and you green card has expired or will expire within the next six months, you may start the renewal process by filing Form I-90, Application to Replace Permanent Resident Card with the USCIS. If your card will not expire for at least another six months and you satisfy all the requirements needed to qualify for citizenship,you may choose to apply for Naturalization instead of renewing your card.
How to Renew a Green Card If You Are Outside the US
If you are outside the US and your card will expire within six months (but you will return within one year of your departure from the US and before the card expires), you can file the I-90 application for your renewal as soon as you return to the US.
If you are outside of the US when the card expires and you have not applied for the renewal card before leaving the US, you should contact the nearest US Consulate, USCIS office, or US port of entry before filing Form I-90.
When to Renew a Green Card
You should renew your card if you are a permanent resident with a card valid for ten years and the card is either expired or will expire within the next six months. However, if you are a conditional resident and your status is expiring, you must use Form I-751, Petition to Remove the Conditions on Residence, to apply to remove the conditions on your permanent resident status.
Abandonment of permanent residence status
A green card holder may abandon his/her permanent resident status by filing form I-407 at a US Embassy. A person who loses permanent resident status is immediately removable from the US and must leave the country as soon as possible or will have to face deportation and removal. In certain cases the person may be banned from entering the US for three or seven years, or even permanently.