Heat stock pot over medium-high heat. Pour in the vegetable oil. When the oil is ready, saute onions until soft. Then, add garlic. Stir a little.
Add the squash first. Cook for 3 minutes, stirring occasionally.
Then, add the bottle gourd. Cook also for 3 minutes, stirring occasionally.
Add tomato, shrimp, water and fish sauce. Mix well. Cover and bring to a boil.
Uncover. Stir. Pour in the coconut milk and mix. Cover.
Turn heat to medium. Cook for 10 minutes.
Remove cover. Stir. Add salt and ground black pepper. Taste. Add more seasonings if needed. Then, sprinkle a pinch or two of chili powder. Mix well.
Place the noodles in the middle. Submerge the noodles by pushing it down using the ladle. Cover.
Simmer for 5 minutes. Uncover and mix well. Remove from heat.
Serve with rice or your favorite side dish.