I don't think the plane reversed course, but it had turned at the last data point from 025 track to 040 track. Now, I need to see what route they filed, because this turn occurred over a fix - from Aviation-safety.net: "Data of flight tracking website Flightradar24 suggest that the flight flew a 25? course towards the IGARI waypoint. Overhead IGARI, at 02:20, the flight changed course to 40?. Last contact recorded by Flightradar24 was at 02:20 at 175 km NNE off the Malaysian coast and 223 km SW off the Vietnamese coast, approximately at the border of the Singapore and the Ho Chi Minh FIR."
The airways DO turn at that point, so the last radar track could have been mid-turn as they were intercepting M765. JUST speculation, but at least I am looking at a chart.
From Avherald.com : "According to the states run Chinese news agency Xinhua Chinese police established that one of the Chinese passengers listed on the manifest never left China, is still at home and in possession of his passport, therefore was not on the accident flight. The passenger's passport had not been lost or stolen, the numbers on his passport and the passport number noted on the manifest are identical however."