The first international travellers for a quarantine-free scheme will touch down in the holiday hotspot of Phuket, as Thailand tries to reboot its depleted tourism industry despite enduring its worst virus outbreak.

Tourism makes up almost a fifth of the economy. But pandemic-spurred restrictions saw Thailand registering its worst performance since the 1997 Asian financial crisis.

The kingdom is pinning high hopes for a much-needed revival on the so-called "Phuket sandbox" -- a model that will allow vaccinated travellers to visit without a quarantine period.

On Thursday, 249 passengers aboard four flights from Israel, Abu Dhabi, Qatar and Singapore are expected to land on the island -- where its sandy beaches have been relatively deserted since the pandemic.

The arrivals come as Thailand weathers its worst-ever Covid-19 wave since an April discovery of fresh clusters -- and the worrying emergence of the Alpha and Delta variants. Nationwide, the current case tally is at 259,301.

But Phuket remains relatively unscathed as Thai authorities have rolled out a mass vaccination campaign in preparation, with 70 percent of residents inoculated with at least one dose.

A command centre tracking foreign visitors' movements via mobile app, which tourists are required to install upon arrival, will also monitor for potential outbreaks.

Despite the fanfare, tourism operators are lukewarm on a robust resuscitation to the island's economy -- which has seen nearly 90 percent of hotels shutter.

"I think the restrictions make people travel less," said Kongsak Khoopongsakorn, president of the Thai Hotels Association Southern Chapter, who also runs a resort on the island.

Besides being fully vaccinated, tourists must remain in Phuket for a fortnight if they wish to travel to the rest of Thailand, and take three Covid-19 tests during this period -- a substantial expenditure for a family.

Kongsak added that authorities had downgraded its sandbox entry forecast of 129,000 visitors in the third quarter to 100,000.

- 'Disappointing' -

Delays in government approval for the scheme has caused headaches for scores of prospective travellers -- who flocked online to air their grievances.

"It is disappointing the communication has been so poor and new requirements without any detail are being created after-the-fact," an American traveller told AFP.

She added she had spent hours phoning consulates across the US to get her paperwork processed -- to no avail.

But even a trickle of visitors will be a lifeline for desperate vendors like Thewan Phromyang, who rents out deck chairs at Phuket's notorious Patong Beach.

"I barely have any income. We can only feed ourselves," the 49-year-old told AFP.

Pre-pandemic, Thailand had expected 40 million visitors to arrive in 2020 -- a far cry from the 6.7 million who made it through strict border restrictions.

Another regional tourist hotspot, Bali, had been eyeing a July reopening, but Indonesian authorities appeared to have backed down as virus cases surge to record levels in the Southeast Asian nation.

While Jakarta has not announced an official cancellation, comments this week from the tourism minister suggested that any bid to welcome back tourists is likely to be delayed until soaring infection rates are curbed.