Carefully trim a very thin slice off the bottom rind of the watermelon half so it sits flat. With a large spoon or scoop, remove the watermelon flesh and place in a bowl, leaving walls of watermelon peel intact. Place watermelon bowl on a plate.
Finely chop reserved watermelon. Finely chop the jicama and jalapeño.
To a large bowl, add watermelon, jicama, and jalapeño along with the chili powder, cumin, onion, cilantro, mint, and lime juice. Stir to combine. Season with salt to taste.
Transfer salsa to watermelon bowl and serve with the chips.