Thailand has dropped rules requiring people to wear masks from Friday, the government said, as Covid-19 cases fall and the tourism-dependent kingdom seeks to lure back foreign visitors.

Face masks had been compulsory in public since mid-2021, when the country saw a wave of cases driven by the spread of the Delta variant.

But the kingdom is keen to kickstart its stuttering economy and is relaxing Covid-19 restrictions, including discarding most entry requirements from next month.

"Wearing a surgical mask or cloth mask is a voluntary practice," said Prime Minister Prayut Chan-O-Cha in a royal gazette announcement issued late on Thursday.

The health ministry recommends people continue to wear face masks in crowded or poorly ventilated areas, the statement added, but there was no explicit mention of public transport.

The capital Bangkok's privately-owned metro service later announced, however, that it would still require travellers using its trains to wear masks.

While the shift was not immediately obvious on the streets of the city, many voiced approval for the policy change.

"The lifting [of restrictions] would allow people to resume their normal life," said Supanya Pajaree, a 26-year-old freelance worker.

American tourist Jake Lucchi was supportive of the move, but said he would continue wearing a mask.

"I usually don't wear one but now I see most people are wearing one so I want to be respectful [to] what people are doing," he said.

The Thai government's move comes after Singapore and Cambodia also discarded rules requiring outdoor mask wearing.

It also comes ahead of the end of the "Thailand Pass" system, which required visitors to register and show proof of vaccination before entering the kingdom.

From July 1, tourists will only have to carry their vaccine certificates or take a Covid-19 test on arrival. (AFP)