3. The following persons shall be persons subject to military law and this Act shall, subject to such exclusions or variations in relation to non-uniformed servicemen as may be prescribed, apply to them:
regular servicemen and full-time national servicemen in the Singapore Armed Forces from the time their liability to report for enlistment or service arises until such time as they are lawfully discharged or released;
operationally ready national servicemen from the time that they are ordered to report for enlistment or service, whether they have complied with such order or not, and while in uniform or performing service in the Singapore Armed Forces or the People’s Defence Force pursuant to section 14 of the Enlistment Act (Cap. 93), and while called out for mobilised service pursuant to sections 16 and 17 of that Act or when called out to duty in aid of the civil power;
all civilians who are in the service of the Singapore Armed Forces when engaged on active service;
all civilians, not otherwise subject to military law, who are followers of, or accompany, the Singapore Armed Forces when engaged on active service;
officers and soldiers belonging to a Commonwealth or foreign force when attached to or seconded for service with or otherwise acting as part of or with any portion of the Singapore Armed Forces; and
volunteers during the period that they are ordered to report for service, whether they have complied with such order or not.