Lindsay Lohan -- Shawn Holley Demands Payment

Shawn Holley is no chump ... she agreed to represent Lindsay Lohan again with one big string attached ... that she gets the $150,000 that Lindsay owes her for prior work ... TMZ has learned.

Sources connected with Lindsay's team tell TMZ ... when Lindsay was on the verge of being on the receiving end of an arrest warrant last week, they called Shawn and pleaded for help. We're told Lindsay herself made multiple calls begging Shawn to come back.

Our sources say Shawn made it clear ... business is business. She said she would rep Lindsay again ONLY with assurance the debt would be wiped clean, and quickly. Shawn demanded a specific payment schedule, earmarking money that Lindsay was slated to get.

What's more ... sources say Shawn got documentation earmarking certain paychecks Lindsay will be getting -- paychecks that will now go to Shawn. In other words, Lindsay will never have access to that money so she can stiff her again.

And sources say Shawn -- whom Lindsay fired just a few months ago -- nailed down how she would be paid for future services.

We're told Lindsay happily agreed to Shawn's financial demands ... frankly she had no other choice.

Let's face it ... Lindsay has an M.O.. The question -- has Shawn outsmarted her this time?

Holley could not be reached for comment.