Prepare ingredients: mince 1/2 onion and 5 cloves garlic; chop 1 large tomato and 2 tbsp fresh cilantro; peel and dice small the 8 oz (1 large) potato; pat the 6 skinless chicken thighs dry.
Heat 1/2 tbsp olive oil in a large deep skillet over medium heat until shimmering.
Add the minced onion and garlic to the skillet and sauté until softened and fragrant, about 2 minutes.
Add 1/2 tsp roasted cumin, 1-1/2 tsp garam masala, and 2 tsp curry powder; stir and cook until the spices are fragrant, about 30–60 seconds.
Add the chicken thighs to the pan and season them with kosher salt to taste. (If you like, brown the chicken briefly, about 1–2 minutes per side.)
Add the chopped tomato, chopped cilantro, 1/2 cup light coconut milk, and 2/3 cup water. Stir to combine and bring to a gentle simmer.
Cover the pan, reduce heat to medium-low, and simmer until the chicken is cooked through, about 25–30 minutes.
Add the peeled, diced potato to the pan, season with additional kosher salt to taste, cover, and simmer until the potatoes are tender, about 10 minutes. Uncover and adjust seasoning before serving.
Pressure-cooker alternative (use instead of steps 5–8): After completing step 4, add the chicken thighs and season with kosher salt to taste, then add the chopped tomato, chopped cilantro, 1/2 cup light coconut milk, and 2/3 cup water. Seal the pressure cooker and cook on high pressure for 15 minutes, perform a quick pressure release, open the cooker and add the diced potato, reseal and cook on high pressure for 5 minutes, then allow the pressure to release naturally. Open, check that the chicken is cooked and potatoes are tender, and adjust salt to taste.