Ryōi obtained a formal trade license, a shuinjō, from Toyotomi Hideyoshi, and managed overseas trading operations, importing goods from southern Vietnam. After Hideyoshi's death in 1598, Ryōi became a trusted advisor and supplier to Tokugawa Ieyasu, who became shogun in 1603, and continued his overseas operations, with a shuinjō granted by Ieyasu.
Between 1605 and 1611, he also played a major role in constructing canals and making the rivers of Kyoto more navigable, so as to better ship goods to, from, and within the city. These included the Tenryū, Takase, Fujigawa, and Hozu rivers; in exchange for his efforts, the Suminokura business was granted extended shipping rights within the city.
Ryōi's sons Suminokura Genshi and Soan followed in their father's footsteps, and took over the family business after his death, enjoying considerable prosperity until the imposition of maritime restrictions by the shogunate in the mid-1630s, when trade with Vietnam came to an end.