Selena Gomez' Alleged Stalker -- In Custody ... Again

Selena Gomez' alleged stalker has been handcuffed by LAPD detectives and he's being interviewed by them right now.

As TMZ first reported ... detectives from LAPD's Threat Management Unit want to speak with Thomas Brodnicki, hoping to place him on a 5150 mental health hold.

Brodnicki was released just before midnight, after a judge dismissed felony stalking charges against him.

Detectives believe Brodnicki -- who has told detectives and a shrink he's spoken with God about killing Selena -- is a real threat to the singer.

Based on Brodnicki's conversation with our cameraman, it's likely cops will indeed 5150 him.