Re-entry Permit: would you advise, if multiple re-entry permit starts counting from the day applied (and not for a calendar year Jan-Dec)

Hey guys, I am currently on a non-immigrant B visa for 3 months before getting my work visa sorted and planning some trips outside of Thailand. I know that if get out of Thailand without a re-entry permit...I'll have to start my non-immigrant B visa process all over again (which I really want to avoid). I want to travel several times outside of Thailand during these 3 months. What is the easiest way to do a re-entry? I know that you can do it at the airport...but can you do that several times? Is the visa counter before or after the immigration? Thanks a lot for your help!