'Saharat Thai Doem' or 'The Federated Original Thai (States)' was a territory in Burma's eastern Shan State and eastern Karenni state approximating to territories ceded under pressure by Siam to the British in 1893 and considered 'lost territories' by subsequent Siamese and Thai governments.

In 1942 the Imperial Japanese Army accompanied by the Thai Phayap Army invaded Burma's Federated Shan States from Thailand. Following the Japanese-Thai victory; on 18 August 1943 the Japanese government agreed to the Thai annexation of all of Kengtung State and part of Mongpan State. The Thai authorities remained in possession of these occupied territories until the defeat of Japan in August; 1945; when the Thai Phayap Army withdrew back to Thailand.