Thailand turned over some newish radar data (not before now because "nobody asked for it") that corroborates the data that the flight turned back toward Malaysia. According to this report, it seems that the flight turned back toward Kuala Lumpur (where it originated) and then later turned west toward Butterworth. A quick look at Google and Earth and I see that Penang International Airport is just to the other side of Butterworth, Malaysia and has a runway about 2 miles long that could probably facilitate that plane. I think it's starting to really look like something major went wrong equipment onboard and those guys were trying to get it back on the ground. Something happened on the way that saw it pointed further west out over the Indian Ocean and unmanned.
