I am coming into this convo VERY late and nothing has been posted for a while, but I still want to answer, lol.
Thingol was murdered for being in possession of the Necklace of the Dwarves.
Thanks for joining, but be more specific. Not exactly. But you're close. The necklace of the dwarves, or the Nauglamir as it was called, was made by the dwarves for Finrod the elf. It was set with many gems by Finrod and later came to Turin, who gave it to Thingol as a gift. Thingol had the dwarves of Nogrod to refashion it and place the Silmaril in it. Thus the dwarves killed Thingol, not only because he was in possession of a necklace that had been made by them previously, but also because of their deep desire for the Silmaril that was set in it. They slew him to obtain to wonderful jewels in the necklace and above all, the Silmaril.