The posting in AVHerald's chat with the AN26 observation seems to have disappeared, but
here is a Vietnamese site which tells essentially the same and looks credible enough. It is apparently from the official Vietnamese search HQ, and there is even a picture of the search area division between Vietnam, Malaysia and Singapore.
Apart from the oil slick, the AN26 also reported an unspecified smoke sighting some 10 miles south of the oil slick and approx 28 NM / 312 degrees from the FR24 LKP.
Airborne search was terminated because of local sunset, but ships are continuing during darkness.
I'm still puzzled because an oil slick 45NM from LKP indicates to me that the plane would have been at least somewhat flyable, but the smoke debris 10 NM away indicates some parts have separated in the air.
Of course this may all still be false spottings and conclusions. Tomorrow will tell more.
Anyone knows the sea currents in the area? A 2 kts current during 12 hrs would account for a 24 NM drift, but to drift 45 NM the current needs to be almost 4 kts which is not that common.