The car and the cement truck were both heading along Patak Road over Karon Hill when the double-fatality crash came on a curving section in rain about 5pm.
Little is known about the man and woman at this stage. Their bodies were being extracted late today.
The car carried Bangkok plates and additional Malaysian numbers of the kind assigned when cars are driven across the border.
A pickup skidded into the rear of the flipped concrete truck without additional serious damage being caused.
* It has since been revealed that just one person, Phuket expat Philippe Wagner, 46, from Switzerland, was killed.