With a yellow crowbar, obviously.

He would become Black or Yellow Lantern, I think. Otherwise, Idk.

Laughter would be something like happiness, right? I suppose Joker could be in line to be a Gold Lantern

Plus didn't a former Gold Lantern lose his sanity?

Plot Induced Stupidity.

Easy, Joker becomes a Yellow Lantern or gets a connection to the Negative Speed Force and then uses Joker Gas, I'm Also Pretty sure Joker has defeated Hal in the Comics (Correct Me if I'm Wrong)

How the **** is he supposed to get a connection to the negative speedfroce. That isn't even possible for him.

Plot

It would make more sense to turn Hal into the Joker so Joker exists twice and once he is hal and hal is him he destroys Hal from the inside and then starts cloning himself to have an army of Jokers.

@Elaexy ^^^🤣

Joker kills himself and turns Hal into the lantern that laughs