Gunner Asch wrote:

Or you can buy/rent/borrow a good STRONG shock collar and watch him
coming..the moment he hits the yard..push the button and hold it down
while he goes into spasms and apparent convulsions. Hold that button
down for more than 30 seconds!! Have his owner shout NO!!! repeatedly
while doing it..then let up and let the owner continue to shout NO!!
until the dog recovers and runs home.

It may..may take 3-4 such treatments before its burned into his brain
that coming over to your place hurts and is a Bad Thing (tm)

And he will try coming onto the property via several different
directions after lighting his ass up the first time

Except for the duration suggested, this is the most humane, and also the
most effective method. Since OP is willing to work with the neighbor, there
shouldn't be any problem in implementing it, either.

I will add that the dog likely doesn't need to be shocked for 30 seconds, as
a few seconds of pain achieves the same result, especially when coupled with
with a stern verbal reinforcement from the owner.

Jon