There are four Orthodox churches in Singapore, but they are all under different Churches.
St Mary and St Mark Church is under the jurisdiction of the Coptic Diocese of Sydney.
Holy Resurrection Orthodox Christian Church of Singapore is under the jurisdiction of the Orthodox Metropolitanate of Hong Kong and Southeast Asia, Ecumenical Patriarchate of Constantinople
St Thomas Orthodox Syrian Cathedral is under the jurisdiction of the Malankara Mar Thoma Syrian Church.
Mar Thoma Syrian Church is under the jurisdiction of the Mar Thoma Syrian Church of Malabar, Diocese of Malaysia and Singapore. This 'Eastern' Church is peculiar because they are in communion with Anglicanism. In a sense, they are Eastern Protestants.