Step 1

Remove zest from lime in wide strips with a vegetable peeler. Cut lime in half; set aside. Bring zest, garlic, coconut milk, and fish sauce to a simmer in a large skillet over medium heat. Arrange shrimp in skillet in a single layer and cook, maintaining a bare simmer, until opaque and pink, about 3 minutes. Using a slotted spoon, transfer shrimp to a large shallow bowl and let cool.

Step 2

Increase heat to high; cook coconut milk until thick but pourable (similar to the consistency of runny honey), about 5 minutes; remove from heat. Remove and discard lime zest and any shrimpy bits. Season coconut sauce with kosher salt and pepper and let cool in pan.

Step 3

Squeeze juice from a reserved lime half over shrimp and spoon coconut sauce over. Top with red onion, jalapeño, tomatoes, and cilantro. Squeeze remaining lime half over. Drizzle with a little oil, then top with tortilla chips and sprinkle with sea salt.Do ahead: Shrimp can be cooked and coconut sauce can be made 1 day ahead. Transfer to separate airtight containers; cover and chill.