By Agence France-Presse
The bay, circled by dramatic limestone cliffs on Ko Phi Phi Ley island, was made famous by the 2000 film starring Leonardo DiCaprio.
But the movie prompted hordes of tourists to sweep in on a daily of flotilla of motor boats, damaging the coral ecosystem and eroding the once pristine white sand beach.
Authorities shut the park temporarily to the public in June but later extended the closure indefinitely to let the bay recover.
On Friday park officials shared video of dozens of blacktip reef sharks serenely swimming close to the beach – images unimaginable just weeks ago as tourists jostled for selfies on the white sand.
“Come and count sharks!” the National Park, Wildlife and Plant Conservation Department said in a Facebook post.
“It’s a good sign that Maya Bay has changed and that change is positive,” the post added.
A Thai marine biologist prominent in the campaign to close Maya Bay hailed the shark video as “beyond imagination, unbelievable”.
“How do I feel? Tearful,” Thon Thamrongnawasawat said in a Faceboook post. “At the beginning I never thought [the rehabilitation] would be as good as this in only six months.”
Authorities have not said if, or when, the bay will open.
“The reef will take a longer time to recover,” an official from the National Park, Wildlife and Plant Conservation Department said requesting anonymity.
Thailand’s idyllic beaches are under increasing strain from huge numbers of tourists and accompanying development in remote and fragile ecosystems.
The country drew around 35 million visitors last year.
Many flock to the town of Krabi where boat trips carried visitors to nearby islands replete with opportunities for snorkelling and selfies – among them Maya Bay.