@Billy ****
you're the first person I've ever seen who got an ED Plus Extension <- those are issued AFTER you finish your degree and gives you one additional year to stay in thailand.
As you see the ED Plus extension is indeed "exempt" from requiring a re-entry permit. <- which at least to me means you can exit/re-enter all you want..
Even so, I would certainly talk to the immigration officer when you stamp OUT of the country to make sure they agree and everyone is on the same page.
Congrats on getting that extension (Y)