The Samui Plus scheme risks cancellation if infections double from the current rate, while the upcoming 7+7 island extension plan is postponed until the situation improves, according to the Tourism Authority of Thailand (TAT).
TAT governor Yuthasak Supasorn said after a discussion with its Koh Samui office and Surat Thani province, the reopening plan is still proceeding despite a record high in new infections.
However, if the infection rate grows by two times from the 39 cases recorded yesterday, the postponement or termination of the Samui Plus model will be considered, he said.
The island-hopping scheme after a seven-day stay in Phuket, which was recently approved, has been put off due to the recent spread of virus, said Mr Yuthasak.
Under the Samui Plus rules, if there are more than 20 Covid-19 cases logged at hospitals over two weeks, tourists have to stay in area quarantine facilities.
Ratchaporn Poolsawadee, president of the Tourism Association of Koh Samui, said there are no severe Covid-19 cases on the island at the moment, but the island must prepare more beds to help with caseloads from hospitals.
Hotels are converting into "hospitels" with more than 200 beds for patients with mild symptoms.
If total cases at hospitals reach 40 within two weeks, the Covid-19 Center of Koh Samui plans to implement more stringent measures, or it could revoke the whole plan, said Mr Ratchaporn.
The island is conducting a search to find people who visited Speedy Lounge & Bar on Lamai beach and Black Bamboo Club, which are linked to one of the new Covid-19 patients.
He said local authorities are taking more decisive action towards businesses that violate the regulations, especially bars and pubs.
"The plan is still to reopen because most new cases were locals, not foreign travellers," Mr Ratchaporn said.
The situation requires close monitoring, said Chattan Kunjara Na Ayudhya, deputy governor of marketing for Asia and South Pacific at TAT.
Koh Samui tightened measures for domestic arrivals from dark red and red zones, requiring negative Covid-19 test results from within 72 hours starting on July 26, even among the vaccinated. Only one foreign visitor tested positive out of 78 total arrivals on the island.