A new and distinct cultivar of Thuja tree named ‘;RLH-GG’;, characterized by its relatively compact, upright and narrowly columnar plant form; moderately vigorous growth habit and moderate growth rate; freely branching habit; dense and bushy form from base to top of the tree; lateral branches that are fine-textured and flexible and resist cracking and splitting; dark green-colored leaves that are soft and fine-textured and tolerate high humidity and high temperatures conditions; and good garden performance.