TMZ has obtained a copy of the suit, filed in L.A. County Superior Court ... which is essentially 12 pages of incomplete, incoherent jibberish.

From what we gather, the man who filed the claim, Thomas A. Green, alleges Lohan communicated with him via Facebook and led him to believe she would participate in a dot-com business he wanted to create.

It appears Green feels he was duped ... and when he pressed Lohan about her true intentions, he uncovered a conspiracy about the killing of Bin Laden.

In his suit, Green writes, "[Thomas] set out to command [Lohan] to twitter and stated if [Lohan] acknowledges this is an Osoma Bin Ladden op all civilians in past wrong doing will receive clemency."

Green also claims he is a former U.S. Marine -- who recently spent time in a homeless shelter due to a "depreciated stage of delusion and hallucinations."

Then, for no apparent reason, he writes, "[Lohan] might be a high end prostitute."

Green is suing Lohan for engaging in unfair business practices -- and he's demanding $300,000.

But as crazy as his lawsuit seems, Green hired a process server ... who served Lindsay at her progress hearing in L.A. this morning.