The British government on Monday will add Thailand to its travel "red list".
Foreigners are banned from travelling to England from red list countries, and nationals are required to quarantine.
"Thailand and Montenegro will be added to the red list from 4 am on Monday 30 August 2021," reflecting the increased coronavirus case rates in those countries, the Department for Transport said.
British and Irish nationals and those living in the United Kingdom are allowed to travel from red list countries, but must quarantine in a hotel for 10 days on arrival.
Thailand will move to the red category as low vaccination levels leave Asia vulnerable to new coronavirus variants, along with Montenegro.
