H1B Extension Issue- started working with my previous employer and filling extension

I worked for employer ““A””, I transferred my H1 and started working for employer ““B”” . Now i joined back my employer ““A”” and it has 1 month H1 Visa validity. Can my employer ““A”” file extension with my most recent pay stubs (from Company ““B””) ?

Yes, they can do that and use most recent payslips (even if they are from B). They should also submit B’s petition to show that you were working for them legally.