In a pot of boiling water, add dried spaghetti and 1 tsp salt. Cook for 6-8 minutes. Set aside, reserving the pasta water.
In a pan on medium heat, add 1 tbsp cooking oil. When hot, add lemongrass and garlic. Stir-fry for 1 minute.
When the garlic turns translucent and the lemongrass is soft, add in 1½ tbsp nam prik pao, 2 tsp fish sauce and cherry tomatoes.
(If you prefer a spicier version, chop some chili padi and add it into the dish along with the garlic and lemongrass.)
Add ½ cup of the cooking water from the pasta and bring to a simmer.
Pour in clams and cover for 5 minutes. The clams should open, but remove any that remain closed.
Add in cooked pasta and mix well. Add kaffir lime leaves and some of the basil leaves, toss until well mixed and remove from heat.
Garnish with remaining basil leaves and serve hot.