You need to submit EVL from your current or prospective employer to state that you are still working in the same or a similar field or a job in the same/similar field is waiting for you once your 485 is approved when submtting the 485 supporting documents. If you intend to go back to your previous employer who offers you a job in the same/similar field as stated in your 140 petition after 485 is approved, then the letter from him or her is OK. If not, it is a fraud. The green card might be revoked.