For the “meatballs:” Adjust oven rack to lower-middle position and heat oven to 350 degrees. Start by whisking chia seeds and water so they have time to thicken up before you add them. Measure the remaining “meatball”ingredients, including cilantro, sriracha, lemongrass, and sesame seeds, in a large bowl; whisk thickened chia mixture and add to the bowl. Using hands, mix thoroughly to combine. Divide mixture into approximately twenty-four2-tablespoon portions, rolling each into a ball.
Meanwhile, bring 2 tablespoons of the oil in a large (12-inch) oven-proof skillet over medium-high heat. When whisps of smoke start to rise from the pan, reduce heat to medium, add balls and cook until well browned on one side, about 3 minutes. Turn the balls over and continue to cook on the remaining side until well browned, about 3 minutes longer. Transfer skillet to the oven and bake until balls are firm, about 25 minutes.
For the sauce: Mix all ingredients and 1/2 cup water in a medium saucepan. Bring to a simmer; continue to simmer to blend flavors and slightly reduced. Spoon over “meatballs” as well as accompanying rice or noodles and vegetables.