Fearing a spread of the Omicron variant, the country had reinstated a mandatory quarantine at the end of December.
But only a few thousand cases are officially recorded each day and the death curve remains stable.
These data prompted the authorities to reassess the situation.
From February 1, vaccinated visitors will now have to provide a negative Covid test carried out in the country of origin, take a second on arrival, and a final one on the fifth day, said Taweesin Visanuyothin, spokesperson for the center of coronavirus management.
Tests on Thai soil must be carried out in an approved hotel.
If the result is negative, the traveler will be able to move freely in the country. "If there is an increase in cases, the situation will be reassessed again," said Taweesin Visanuyothin.
After more than 18 months of closure, the kingdom had reopened its borders in early November to vaccinated tourists on presentation of a simple negative PCR test.
A few tens of thousands of visitors had taken advantage of this easing of restrictions.
Before the pandemic, the country was one of the most visited in the world with nearly 40 million arrivals in 2019.
The Ministry of Tourism hopes to welcome five million visitors this year.
© 2022 AFP