@chuckindenver

My theory is that your M1903 was one of the rifles received by the Chinese Nationalists as military aid during WW2. During the war the barrel was damaged and replaced by one of the Chinese arsenals under Chiang Kai Shek's control in 1946. In 1949 she followed Chiang and his Nationalist army to exile on the Island(s) of Taiwan a.k.a. Formosa.
When the Garands were replaced by a localy made version of the M14icon in the sixties the M1917's, M1903's, M1's and M1928's were sold to an other country. Maybe Thailand?

Why do you think it is a Thai M1903?