EXCLUSIVE

Y'know what they say about stranger danger -- the chick who pulled a knife on Eddie Kaye Thomas had just met the "American Pie" star less than 24 hours earlier ... TMZ has learned.

As we first reported ... SWAT responded to Thomas' house Wednesday evening after Thomas called 911 ... and remained in a standoff with the woman for a couple hours ... before forcing her out with tear gas.

She was taken into custody, checked out at a hospital, and then booked for felony vandalism.

But here's the best part -- according to law enforcement sources Eddie met the chick the night before at Mel's Diner, and brought her back to his place.

Typical one night stand, we're guessing ... until Wednesday afternoon when Eddie says they got into an argument, and she pulled the knife.

During the standoff, we're told the woman smashed up a phone, a guitar ... and generally trashed Eddie's house before cops smoked her out.