Sean Kingston continues to have trouble holding on to his bling.

Late last year, Kingston claimed his jewelers kidnapped him and took back a watch he was buying from them.

Now it looks he's lost his 300K chain in a more traditional way: It was snatched from him during a brawl in the club.

According to a police report seen by TMZ : "Two suspects approached Sean inside Penthouse Nightclub & Dayclub in L.A. and somehow the altercation turned physical ... they began punching him before one forcibly took the pricey chain."

Somebody in Kingston's camp called in the robbery on Sean's behalf, but by the time the cops arrived Kingston and both suspects had left the club.

Police are continuing to investigate.