green card received but...

I applied I-140/I-485 from company A but for economical reasons (low salary) I was forced to move to company B before the I-140 approval. I received yesterday notice of approval I-140/I-485 and notice of welcoming new resident and card ordered from company A. What are my options now ?. Can I work part time with company A without leaving company B for legitimize the greed card? or may I return the green card to UISCIS and continue to the process that company B started again?.

I would make sure you have legal counsel review your details and then advise you but you may have to return and process again. Not sure you should have made that move to B at that time though so check the legal effect of that.

Green card is for FUTURE EMPLOYMENT. To be on the safe side, you should
work for company A NOW instead of RETURNING YOUR GREEN CARD. Assuming your Company A is a contracting company. Once you join Company A, He MUST pay you the salary (as mentioned in your labor notice) even you are in bench (no project contract). Based on current market situation, there is a good chance you Company A might not offer you a job. Under this situation, your green card is safe.

This is my personel opinion, please hire an attorney.