Churches of Kerala follow the tradition of Syrian Christians known as Malankara Christian Orthodox Church.
St. Thomas, disciple of Lord Jesus Christ, is claimed to have visited India and founded eight churches in Kerala, the foremost being St. Mary's Church at a place called Niranam near Thiruvalla. It is a Historical Monument today and many ancient relics are still preserved in the museum there.
References
Churches of Kerala Wikipedia(Text) CC BY-SA