Li
nk to an online version (pdf) of the 18th century edition to which St. Nikodimos of the Holy Mountain refers in his Synaxarion entry for St. Ephrem. It is comprised of three volumes of Syriac writings and three volumes of Greek writings. All six volumes are accompanied by Latin translations, which makes both corpora even more accessible.
http://contentdm.lib.byu.edu/cdm/ref/collection/CUA/id/27186
Saint Ephrem the Syrian 