Combine all chili oil ingredients in a small saucepan and heat over medium heat. After 2–3 minutes, when the oil is hot and the chilies begin to gently bubble, reduce to low heat and simmer for 40 minutes.
Remove from heat, cool to room temperature, then strain into a glass container and discard the solids.
Submerge the kale in water, then rinse and drain thoroughly. Remove the bottom portion of the thick stems and slice the leaves into 1-inch (2.5 cm) ribbons.
Transfer to a mixing bowl with the olive oil, vinegar, thyme, and black pepper. Massage for 60-90 seconds until the leaves are tender and evenly coated.
To make the seitan, warm the olive oil in a skillet over medium-high heat. After 90 seconds, when the oil is hot, add the seitan and cook, flipping the pieces regularly, for 7-8 minutes until lightly browned and crisp all around.
Whisk together the tomato paste, chipotle powder, ground chili, vinegar, and water in a small bowl.
Add the marinade to the skillet and stir to coat the seitan evenly. Continue cooking over medium-high heat until most of the liquid has reduced and absorbed into the seitan.
Heat a large skillet or griddle over medium-high heat. Brush both sides of a tortilla with chili oil and place it on the hot surface. Cook for 30–40 seconds until it begins to bubble, then flip.
Add the kale, arugula, kimchi, and hot seitan. Cook for 40–60 seconds until the underside is golden brown.
Transfer to a plate and fold into a triangle, leaving one side open. Repeat with the remaining tortillas and filling.