I don’t think the toothpick is actually behind the bill (I don’t see how he could have gotten it behind the bill and if you look at the frames at 1:17 and 1:18, it seems to be in between the fold).
My guess is there is another small toothpick involved. If so, where does he hide it at the end?
There’s a split in the wood of the poker, so that part of the bill can be pulled up into the slit and give the appearance that the pick is inside the bill, but the point remains behind.
In this video too? It doesn’t look like it can be done with a split in the toothpick. 
Yeah, it’s a split in the pick. Thanks!
The pick is split into two points, but the key is that one point (the one that sits inside the fold) is shorter and blunt, and the other point (which lies behind the bill) is longer and sharp. Thus when the pick is pushed down, the sharp point projects below the bill while the short/blunt point rests in the fold.
In case anyone hasn’t already noticed,you can see it clear as day at 0:41.