John Gill Commentary 1 Kings 16:6

"And Baasha slept with his fathers, and was buried in Tirzah; and Elah his son reigned in his stead." — 1 Kings 16:6 (ASV)

So Baasha slept with his fathers
Or died, not a violent, but natural, death:

and was buried in Tirzah ;
where was the royal palace of the kings of Israel:

and Elah his son reigned in his stead ;
yet but a short time.