Her technique involves the reduction of complex scenes into basic geometric forms. She used large, flat areas of colour to build her compositions. The parasols in her terrace works are circular elements that organise the entire image rather than mere functional objects. This method creates a sense of stillness. Her figures are often static, positioned to create a balance between the human form and the surrounding architecture.

Modern collectors value Thies for her clean aesthetic and her ability to evoke a specific era without excessive sentimentality. Her prints work well in rooms with minimalist furniture. The palette she chose is often muted, which allows the structure of the drawing to remain the main interest. Her work provides a calm presence on a wall, suited to those who prefer art that is both figurative and abstract in its construction.