"Thomas Merton's approach to photography, and one of the reasons his photography is truly personal, lay in his use of his lenses primarily as contemplative instruments. He photographed the things he contemplated. His "serious work," as he called it, is meditation. He did not seek to capture or possess, and certainly not to arrange the objects he photographed. He lent his vision and his lenses to them in a real way: he was there and he did the mechanical things - focusing, composing - but he allowed the objects to remain true to themselves and to reveal themselves, and he trusted that "the connections would somehow be made."
"Merton distinguished between his serious work and the documentary uses he made of photography. In the latter, he captured faces and places and events as any good photographer would, though with his own personal characteristics of wit and composition. In the serious work he was captured by the play of light, the ambiance, and the inner life of the things he photographed.
"Finally, for him, the best images were the silent but communicative. In his writing he used words, with their implied sounds, to explore and express silence. He struggled toward an expression of silence through the visual image, in photographs that communicated the essence of silence without any implied sounds. In this he worked as a painter might, approaching his goal through many photographic sketches and studies."
- John Howard Griffin, from "The Hidden Wholeness" pp 4-5
Merton started out with an Instamatic camera - the photo over on the right - the only known photo of God - was made with that camera (according to Jim Forest). As he became more interested in photography he borrowed better cameras, mostly from his photography mentor and friend, John Howard Griffin. Griffin told him that he would never get much satisfaction from his work until he got a good camera. Merton responded that he had taken a vow of poverty and did not want to ask permission to buy a camera. Hence, the arrangement whereby Griffin loaned him "in perpetuity" some good cameras.
In the book, "The Hidden Wholeness", John Howard Griffin mentions a Roleiflex and I believe it was a Leica that Merton took to Asia with him. A closer look at the photo on the right above - looking at Merton looking - the letters on the camera read: ALPA. I'd guess that those were about the best cameras that could be had at the time.
Merton published few of his photographs, but during the last 3 years of his life he was photographing steadily and built up a large archive. He sent his undeveloped film to John Howard Griffin, who developed and stored it in his darkroom archive.