The unidentified patient had recently returned from Africa, where the virus has caused a deadly epidemic, health officials said.
The authorities said the risk of a rapid spread remained low because the new cases had had household contact with the first infected person.
The decision is a crucial step in getting shots to the Democratic Republic of Congo, the center of the outbreak.
The 100,000 doses of the MVA-BN vaccine, manufactured by the Danish company Bavarian Nordic, have been donated through HERA, the EU's agency for health emergencies.
It is not easy to witness people battling an mpox infection. Fear and stigma make it difficult for patients to seek medical attention soon after symptoms...
Officials are testing if the patient has the new version of the virus. If confirmed, it would be Thailand’s first case involving Clade Ib mpox.
It was not clear if the patient had contracted the new, potentially more deadly strain of the disease, which first appeared outside of Africa in Sweden...
The World Health Organization declared a global health emergency over an outbreak that has spread to more than a dozen African countries.
The epidemic is concentrated in the Democratic Republic of Congo, but the virus has now appeared in a dozen other African countries.