Soak pinto beans in water for 4 hours, changing water every 30 to 45 minutes; drain.
In a large pot, bring 6 cups of water to a boil. Add pinto beans, ham hock, and kosher salt. If needed, top up with more water to submerge ingredients by at least 1 inch.
Simmer on medium-low heat until beans are tender (2 to 3 hours).
Remove ham hock from the pot; chop the meat and return it to the pot.
Combine tomato sauce and brown sugar with the beans. Continue simmering until beans are tender and flavors meld (about 1 more hour).
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