SOMETHING remarkable is happening on the ever-remarkable Andaman Sea coastline.

The tsunami shore has in the past 12 months seen boatpeople pushed out to sea to drift and sometimes to die, and also been declared ''the best five-star destination of 2009'' by the New York Times.

And now, a big mother leatherback is back.

Weighing as much as 300 kilos and stretching to two metres wide, this giant has been coming ashore in the past few weeks at one specific location in ''Greater Phuket'' regularly, to lay eggs.

Marine biologists have been recording the visits of the leatherback to the Phang Nga beach. She only comes back to lay eggs every 25 years, and her time is now.

Remarkable old photographs of giant leatherbacks laying eggs, once thought to be a record of a natural process that would never be seen again, are no longer simply a part of history.

New photographs are being taken as the leatherback comes ashore in a 12-day cycle. In December, she left 99 eggs in the sand. In early January, she left 113.

Biologists know she will be back soon to leave more eggs.

And the hatchings should begin to take place from February 24, with the second batch due to hatch in early March.

The leatherback will return five or seven times, every 12 to 15 days, each time depositing more eggs.

Parrob Plannga, head ranger of the Forests Office in Phang Nga, says the site of the hatchings is being watched day and night to protect the eggs.

''Last year we had just one leatherback turtle appear and lay eggs just once,'' he told Phuketwan ''This turtle is larger and has so far kept to her egg-laying pattern.''

Leatherbacks go back 150 million years, he said. ''They will return to the beach where they hatched just once every 25 years,'' he said.

''We can't care for their eggs in a hatchery because of the characteristics of the hatchlings.

''The young leatherbacks don't swim in circles, they swim in straight lines, so they keep hitting the walls, and eventually die.''

Biologists are concerned that the leatherbacks may be laying more female eggs than males because they can tell from the laying-point on the beach whether each batch is predominantly male or female.

The first year or so of the life of most Andaman coast turtle species remains a mystery.

Once home to five species, Phuket no longer has any turtles hatching on its shores because of increasing coastal development, noise and light.