Nine Ki-21-Ia/b's were sold by Japan to Thailand in 1940 for use by the Royal Thai Air Force against Vichy French forces in French Indochina but did not participate in the French-Thai War as its crews had not completed training.
Sembilan Ki-21-Ia/b's dijual kepada Thailand pada 1940 untuk digunakan Angkatan Udara Kerajaan Thai melawan Prancis Vichy di Indochina Prancis tetapi tidak akhirnya tidak terlibat dalam Perang Prancis-Thai karena para awaknya belum selesai dilatih.