Search area thus very large and uncertain, since if military radar info is correct plane turned west from Gulf of Thailand and overflew Malyasia or Thailand before being detected in the Malacca strait off Malaysia's west coast. If plane was flying low as last military radar contact suggested, then it could have continued flying low and have traveled away from the last location.
Map
Map: Malaysia Airlines Flight 370
However, I am wondering how reliable the Malaysian military radar contact is. If they did detect a plane, how did they identify it as the 777 in question?
Unfortunately, the ocean on the west side of Malaysia is much deeper than the Gulf of Thailand. 1000 meters with some 4000 meter depths. If the plane did crash into the ocean there, the delay in searching that side of Malaysia will mean debris has dispersed more, beacon batteries may be getting drained.