The government expressed confidence on Monday that Covid-19 can be controlled for travellers arriving by air, but not for people crossing illegally into Thailand by land.
Apisamai Srirangson, a spokeswoman for the Centre for Covid-19 Situation Administration, said that in the first week since reopening on Nov 1 there were 22,832 arrivals at airports, of whom only 20 tested positive for Covid-19.
The largest number of arrivals were from Germany, with 2,666 visitors, followed by the United States (2,665), the United Kingdom (1,475), Japan (1,449), South Korea (987), Russia (949), Sweden (817), France (774) and the United Arab Emirates (565).
The arrivals included 14,278 visitors who entered the "Test & Go" process without quarantine, having been fully vaccinated against Covid-19 and arriving from low-risk countries at Suvarnabhumi, Chiang Mai, Phuket or Samui airport.
Another 7,483 entered the Sandbox quarantine process during the first week. Most of them, 6,710, arrived in Phuket. There were another 1,071 arrivals who were not fully vaccinated and entered quarantine for either seven or 10 days.
"The 20 infected visitors made up just 0.09% of all arrivals," Dr Apisamai said.
Government spokesman Thanakorn Wangboonkongchana said the number of infected visitors by air was at a controllable level and the government was satisfied with the situation.
The Tourism Authority of Thailand predicts 300,000 visitors per month for the last two months of the year, and that would distribute income to many areas in the country, he said.
However, Prime Minister Prayut Chan-o-cha was concerned about the illegal entry of workers, with more than 2,800 illegal migrants arrested over the past week.
"Statistics show that migrant workers were a common cause of Covid outbreaks, especially at markets in Bangkok, Samut Sakhon and Chiang Mai," Mr Thanakorn said.
He urged business operators to hire only legal migrant workers, quarantine them, provide them with vaccination and have them comply with disease control measures.
The government on Monday reported Covid-19 clusters originating from markets in Chiang Mai (65 new cases), Surin, Udon Thani, Phitsanulok, Chanthaburi, Chon Buri, Prachuap Khiri Khan, Ratchaburi, Phetchaburi and Songkhla provinces.
Cases from the clusters were included in the 7,592 new Covid-19 cases recorded on Sunday, with details released on Monday.