During the winter season the beach in Ham Tien is short of sand due to erosion and wind, more wind, less beach, the tide is irrilevant.
After June the winds go away and the sand is back.

The photo was taken in January at 10am with low tide at the center of Ham Tien, the best part, at Sankara sea wall around number 80 so after that number you have booked  a resort with a sea wall, before that number one with a small beach.

In October the steps of the retaining walls are almost completely covered with sand. As with any place in the world there are 2 low tides a day. One is very full the other very low. Within 7 days of these photos the sand would have been much more exposed, varying according to the state of the moon.

Ham Tien 80 East

Sankara, the beach