Airspace and Radar
The Malaysian narrative supports a number of different scenarios. A steady state flight across Malaysia is one way to "evade" radar (by blending in) and evasive fighter pilot tactics are one way to cause someone watching radar to notice. Per MH370 first turn (Igari), Malaysia military radar might have noticed a offshore inbound unidentified target, but apparently it didn't. The next soonest time for a military alert would have been if ATC had notified Malaysian Air Dispatch and an alarm raised because of no contact . As soon as MH370 left Malaysian airspace, it was somebody else's business. The aircraft might have been seen paralleling borders by Thai or even Indonesian radar, but the aircraft might not have been 'noticed' unless it was headed to or over each's respective airspace. In effect, after 30 minutes this aircraft would have been off radar(and not a 'potential threat'), until and unless, it crossed another country's airspace.