Thailand just released radar confirming the turnaround.
Thai military radar data bolsters belief that Flight 370 changed path - CNN.com
The Thai military was receiving normal flight path and communication data from the Boeing 777-200 on its planned March 8 route from Kuala Lumpur to Beijing until 1:22 a.m., when it disappeared from its radar.
Six minutes later, the Thai military detected an unknown signal, a Royal Thai Air Force spokesman told CNN. This unknown aircraft, possibly Flight 370, was heading the opposite direction.
Nothing really new there, but it confirms what was already believed.
This part is interesting though:
"The unknown aircraft's signal was sending out intermittently, on and off, and on and off," the spokesman said. The Thai military lost the unknown aircraft's signal because of the limits of its military radar, he said.
That sounds a lot more like an equipment failure than someone deliberately turning off the transponder.