Born in Bay City, Texas, Thomas became a painter of detailed Southwest landscapes and an art gallery owner in Taos, New Mexico.
He was a professional artist from the age of nineteen and began by painting scenes of the American South including swamplands, cypress and beech trees, and blacks toiling in the field. He also did etching to supplement his income, but discovered that his slightly impaired eyesight prevented him from being a skilled etcher.
In the early 1930s, he began experimenting with sepia-tones and desert painting and developed a sophisticated range of colors, which were particularly expressive of the desert country.
As he was reaching a high point in his career, he had to interrupt it to serve in the Navy during World War II, but he continued painting–this time mixing paints for a camouflage division, which he later joined.
After the War, he settled in Taos, New Mexico, and Bert Phillips, founder of the Taos Art Colony, became one of his best friends, and they took many painting excursions together. He was also the first gallery owner to represent Bill Moyers, one of the early members of the Cowboy Artists of America.
With his wife, Sallie, he founded the Taos Art Gallery, and used this avenue to help local artists find a market for their work. His paintings are in the Gilcrease Institute of American History, the University of Arizona Art Museum, and many private collections.