Do I have to file TD F 90-22.1?

Until such time that you formally surrender your lawful permanent residency of the U.S., you are a resident alien of the U.S. and you must abide by U.S. tax law as it relates to U.S. citizens and residents.

So what does the law says about a green card holder who does not live in the US and has no income from US sources? (Except I am guessing minor interests from the bank account.)

Us citizens and US resident aliens are taxed on their worldwide income regardless of source or where in the world they reside. If one's income is high enough to meet the filing requirement for one's filing status, a tax return has to be filed. This is true even if all their income was excludable as foreign earned income.

is a holder of a green card, who is living not in the U.S. but in his home country, a "US resident alien"?

See my original reply to the OP in this thread. In addition, here is what the US Embassy in just about every country has on their website:

If you have a U.S. green card, you are a lawful permanent resident of the U.S. even if you live abroad. This means you are treated as a U.S. resident for U.S. income tax purposes and you are subject to U.S. tax on your worldwide income from whatever source derived. Accordingly, you must file a U.S. tax return unless (1) there has been a final administrative or judicial determination that your lawful permanent resident status has been revoked or abandoned, (2) your gross income from worldwide sources is less than the amounts that require a tax return to be filed, or (3) your U.S. residence status is affected by an income tax treaty.

I should have added: See IRS Pub 4588, Tax Guide for Green Card Holders.

Yes, you have to file. Be aware that your green expires one year after you have been out of the country, though you can fill in a form and have it expire after 2 years.

green card=us resident

-----> real address on hobokeni or hobokenx

It is more complicated than that. You cease to be a permanent resident immediately if you leave the US with the intention of living abroad permanently. Even after a year he may get a returning resident visa if he demonstrates that he has not abandoned his residence in the US. In the worst case, he would have a chance before an immigration judge if tried to return to the US after an absence of more than a year. It is certainly not something for a tax adviser to decide. The Treasury will happily consider him a US resident if it is more advantageous to them.