LOL is internet for "Laughing Out Loud" a.k.a. a fucking lie.
Anyone who uses "LOL" is either:
a) A middle aged person somehow stuck in late 90s teenager talk thinking it's still relevant
b) Someone who said this in their teens in the late 90s/early 00s and is now being ironic
c) Someone who can't think of any way to answer whatever the hell stupid thing you just said
It is never actually someone laughing out loud.
I use "ha." when I want to be an asshole and show how unfunny whatever attempt at being funny you just said.
I use "haha" when I want to recognize something as being technically funny but not inciting the required reaction to something being funny. This is more a kind of, "I recognize you are trying to be funny, I believe that it is funny but not funny enough for me to even internally chuckle."
I use "hahaha" when something is actually funny and I am chuckling internally.
I use "hahahahahahaha" when I am actually laughing. This is rare.
I have also noticed people putting exclamation points at the end of their haha's. This is stupid. Isn't a hahaha an implied exclamation? If it was a quiet laugh, you should use "heh heh heh." But multiple ha's in a row require no punctuation. The exclamation is understood.
Further, if you put a period at the end of a hahahaha you are implying that you only ha'd four times. This is insincere. A real laugh is uncountable. No one counts how many times they ha'd if it was over three times. And three times, typed, is merely an internal chuckle.
Get this fucking shit right, people.