Can a green card holder re-enter the USA using a TEMPORARY passport issued by his country Embassy? For example, say a Thai national with a green card loses his/her passport while visiting Spain, gets a TEMPORARY passport from the Thailand Embassy in Spain: Can that person board a flight to re-enter the USA using that temporary Thai passport?
Yes, a green card holder can re-enter the USA with or without any sort of passport because a green card is sufficient by itself:
United States (U.S.) LPRs do not need a passport to enter the U.S. as per 8 CFR 211.1(a), however, they may need a passport to enter another country. Please contact the embassy of the foreign country you will be traveling to for their requirements.
While CBP does not require the passport as noted above, the airlines may have their own requirements, please check with your airlines prior to travel. Also, travel documents for LPRs do not need to be valid for any certain amount of time. Your LPR card only needs to be valid on the day that you are entering the US.
LPRs who are out of the U.S. for more than 180 days are subject to new immigrant inspection procedures as per 8 USC 1101.
As to boarding the airplane, the airline will use a database called TIMATIC, which has this to say about travel to the US by a Thai national who is a US permanent resident:
Passengers with a Permanent Resident/Resident Alien Card (Form I-551).
Passengers with a US Travel Document (Form I-327) "Permit to Re-Enter".
Passengers with an Authorization for Parole of an Alien into the United States (Form I-512).
Passengers with an ADIT stamp, (Upon endorsement, serves as temporary I-551 evidencing permanent residency), on a Form I-94.
Passengers with a Transportation Letter.
Nationals of Thailand with a temporary passport.
The green card is formally known as Form I-551; note that it is the first item on the list of documents that entitle the traveler to exemption from the passport requirement.