Employer change with H1b

I was in USA for 6 years and came back to India last year. Now, I am traveling to USA again on same H1b on a new deputation with the same employer. Can I change my employer immediately after my travel? I’ve a approved i140 ( more than 6 month back ) with the same employer.

When you enter the US using the I-797 from your current employer, CBP assumes that you will work for your current employer. If you try changing employer without working even a single day for your current employer, that may be counted as a fraud.
My suggestion is to work for your current employer and then apply the H1B transfer with the new employer after few days.