Help!! Travelling before H1B effective

I am now holding F2 visa, and h1B will be effective on Oct. 1. Since the gap
is 5-month long from now to Oct. 1, the company is planning to send me to Malaysia or other Asian countries for a couple of months. My visa is
still valid unitil December because I just came back to America from China
in Feb.. When I re-enter USA in Sep., do I need to go to the embassy to apply a new visa? If I do, I should apply F2 or H1? Is this going to affect my H1B status? Please give some advice or suggestions. THanks in advance.