Is the data erroneous ?
The primary radar plots from the Malaysian military need to be confirmed with civilian counterparts and other military. If they can't they need to run a live test. Get a B777 and fly it on the SAME track and see what their radar returns are like. They could do this today just coordinate all agencies. Malay, Thai and military.
The area where these returns are reported is high traffic area. Flights to India to Phuket, Langkawi, Penang, Hadyai, Krabi etc etc. Also is this primary radar data accurate, with jumping flight levels sounds like different targets to me.
The Immersat info needs to be made public. Tell us what they exactly have. If it's just dumb keep alive pings it's next to useless. If they have plots they need to come forward.