In April 1862, Thomson left Edinburgh for Singapore, beginning a ten-year period spent travelling around the Far East. Initially, he established a joint business with William to manufacture marine chronometers and optical and nautical instruments. He also established a photographic studio in Singapore, taking portraits of European merchants, and he developed an interest in local peoples and places. He travelled extensively throughout the mainland territories of Malaya and the island of Sumatra, exploring the villages and photographing the native peoples and their activities.