I have been living and working in canada for last 3 years and this year I will not meet the substantial presence test for being a resident alien with regard to us taxes
If I file none resident, will I loose my green card?
I am employed and paid by a canadian company on a 3 year work permit and did not file any paperwork for leave of absence from us as I thought I would be traveling back to the states 4-4 times per year

@ When you have green card, it means you are US resident, so you must file tax as "resident".

@ Without a Re-Entry Permit, your status is automatically revoked after 1 year. I don't think they will let you in.