Defending champion Jazz Janewattananond of Thailand birdied the 18th hole for a sparkling six-under-par 65 to grab the lead at the halfway mark of the SMBC Singapore Open on Friday. On-song Jazz has a two-round total of 10 under 132 and is a stroke ahead of teen sensation Joohyung Kim of Korea, in with a 66, and Filipino Miguel Tabuena, …