Selena Gomez -- Cops Plead With Her ... Just Lock Your Damn Door!

Someone give Selena Gomez a Kleenex, because she cried wolf again ... after cops responded to yet another false alarm.

Law enforcement sources tell TMZ ... an alarmed Selena called police a few days back saying she thought someone was inside her house because when she got home the door was unlocked.

Cops raced over but found no one inside.

This is the third time Selena made calls to cops fearing an intruder where there was none.

Selena had gates installed around the house earlier this year -- after a stalker repeatedly showed up at her $3 million Calabasas mansion.