Its prime minister described it as a calculated risk to revive its troubled economy.
Thailand is to start a pilot reopening its most popular island, Phuket, from July 1st, with other travel hot spots to follow.
Phuket has been vaccinating most of its local population.
In a televised address this week Prime Minister Prayuth Chan-ocha said the goal is to reopen the tourism-reliant country to fully vaccinated travellers without the need to quarantine.
"I know this decision comes with some risk because, when we open the country, there will be an increase in infections, no matter how good our precautions. But, I think, when we take into consideration the economic needs of people, the time has now come for us to take that calculated risk."
Strict entry requirements helped keep Thailand's coronavirus outbreaks under control until recent months.
But it's come at a price.
The country lost about $50 billion in tourism revenue last year - an 82% plunge.
Prayuth urged the public to get vaccinated as fast as possible to help achieve the reopening target.
And said Thailand is ahead of target in securing 105.5 million doses of vaccine for this year.