multiple payroll on h1b

[axbycz3]

Hi,

I'm currently working on h1b (h1b approved until 2018) through my employer at a client place. I got an offer from the client and offered me full time. I have some money with my employer and want to check if i i can run multiple payroll. I won't let my employer know that i have changed until i get my money. Is this legal?