Air travellers arriving in Japan from Thailand and four other countries must enter quarantine for 13 days starting Monday.
The Thai ambassador to Japan said all arrivals from Thailand will be subject to quarantine for three days at accommodation arranged by Japanese authorities after they enter the country. They have to stay at home or another location for 10 more days, it added.
The measures will come into force on Monday and also apply to arrivals from India, Nepal, Mexico and the Maldives.
Thailand and four other countries have been added to the list of countries experiencing an Omicron outbreak by the Japanese government.
Since Jan 15, entrants from all other countries must undergo 10-day quarantine, instead of the previously-required 14 days.
Japan allows only people with permanent residence in Japan, diplomats and people with humanitarian reasons to enter the country. Tourists are not allowed in.