Fill a pot with about 1/3 full of water and add 1 pork-flavored bouillon cube. Bring the water to a boil.

Prepare the Tom Yum herbs: slice and lightly crush the galangal, lemongrass, and kaffir lime leaves, then add them to the boiling water along with the sliced tomato.

Season with a little fish sauce, but don't make it too salty yet since the canned fish is already seasoned.

Once the water is boiling, add the canned fish. Let it boil for a bit without stirring to avoid breaking up the fish and making the soup taste fishy.

Taste and adjust the saltiness. Add the glass noodles and let the soup boil until the noodles soften, then turn off the heat and cover the pot.

Season with lime juice and roughly pounded bird's eye chilies to your preferred level of sourness and spiciness. Finish by sprinkling chopped culantro (or cilantro) for extra aroma. Tip: Add the lime juice after turning off the heat to prevent bitterness.

Ladle the soup into bowls and serve hot with steamed rice, or enjoy it on its own.