Thailand will introduce a $9 entry fee for foreign visitors from April, officials said Wednesday, even as the kingdom seeks to lure travellers back and repair its Covid-battered tourism sector.

Strict entry rules imposed to curb the pandemic hammered Thailand's crucial tourism industry last year, contributing to the economy's worst performance in more than 20 years.

The new 300 baht ($9) charge will be incorporated into airfares, government spokesman Thanakorn Wangboonkongchana said in a statement.

Before the pandemic, nearly 40 million visitors a year flocked to Thailand, but the kingdom is hoping to revamp its tourism strategy with a greater focus on sustainability.

"Revenues will be used for foreign tourists' insurance coverage and infrastructure improvement for sustainable tourism," Tourism Authority of Thailand governor Yuthasak Supasorn told AFP.

Tourism revenues are forecast at $39 billion to $54 billion this year, according to the Ministry of Tourism and Sports -- around $24 billion dollars of which is expected from foreign travellers.

An estimated five million foreign tourists are expected to enter the kingdom in 2022 if current travel patterns remain the same, according to the ministry's forecast -- down from nearly 40 million a year before the pandemic.

Tourists walk on a beach on the Thai island of Phuket
Tourists walk on a beach on the Thai island of Phuket AFP / Mladen ANTONOV

But the tally could rise to 15 million visitors if arrivals from China, India, and neighbouring countries improve.

Thailand eased its entry rules towards the end of 2021 as it sought to reboot tourism, but changed the regulations again as cases of the Omicron variant surged worldwide.

Authorities have extended the suspension of a no-quarantine "test and go" scheme until further notice.

But they have also extended the "Sandbox" scheme, adding three southern beach destinations to the island of Phuket.

Under the programme, fully vaccinated travellers spend seven nights in the sandbox area then can move elsewhere in Thailand -- assuming they test negative for Covid.

A mandatory quarantine period of 10 to 14 days is applied for those who are not fully jabbed.