Thai vs. Vietnamese Fish Sauce: How They Taste and What to Use Them On

I keep two fish sauce bottles in my pantry and I use them for different things. One is Thai-style, fermented with added sugar and sometimes blended from more than one species of fish. The other is Red Boat 40°N, a Vietnamese fish sauce made from a single species, black anchovies, with nothing else added. They come from different culinary traditions, they behave differently on a spoon, and once you cook with both you start to understand why each one exists.

The Difference Is Built Into the Bottle

Fish sauce is graded by nitrogen content, measured in grams per liter. Higher nitrogen means more dissolved protein, which means more flavor. Red Boat 40°N earns its name from that number: 40g/L of nitrogen, which puts it near the top of the Vietnamese grading scale. Thai-style sauces tend to range from 25 to 35g/L, and some of the lower-priced ones add sugar or dilute the ferment to stretch it further.

Red Boat comes from Phú Quốc island, which holds a protected geographical indication for fish sauce — the Vietnamese equivalent of Champagne's AOC. The fish must be local, the fermentation traditional, the barrels wooden. Thai production, particularly the large commercial bottles you find in most Asian groceries, does not operate under those constraints. Brands like Tiparos and Squid Brand are blended for consistency and shelf life, not for a single-origin flavor profile.

What the Spoon Reveals

I poured each one into a small dish and smelled them before tasting. The Thai-style bottle smelled like the inside of a tin of anchovies, but rounder, with a faint caramel note sitting behind the fish. Strong when I first twisted the cap, then it settled. Red Boat opened with a sharper, almost briny smell. Less sweet than the other bottle, closer to low tide than to a fish market. After a minute I could pick out something savory and a little nutty.

Straight off the spoon, both were salty enough to make me wince. The Thai-style one hit the front of my tongue harder. The Vietnamese one felt like it spread out and lingered, with the salt arriving later. Color told part of the story before I even tasted: Red Boat was a clear reddish amber, like weak tea held up to a window. The Thai-style bottle was slightly darker and a bit cloudier.

I could taste the sugar in the Thai-style bottle once I knew to look for it, a soft edge right after the salt. Red Boat had none of that. It went straight from salty to savory and stayed there. The Vietnamese one left a savory, almost brothy aftertaste for a good half minute. The Thai-style one faded faster and left a little sweetness behind.

Raw Uses: Where the Bottles Diverge

I mixed the same ratio of lime juice, sugar, minced garlic, and sliced chili into each to make nuoc cham. With Red Boat I used less sugar and it tasted cleaner; the lime and garlic stayed distinct. The Thai-style version came out rounder and sweeter, almost like a sweet chili dip, so I skipped the extra sugar the second time. My pick for a dipping sauce: Red Boat, because I could control the sweetness myself.

For prik nam pla, I sliced a few Thai chilies into lime juice, added a crushed garlic clove and a splash of fish sauce, and spooned it over a fried egg on rice. The Thai-style bottle felt more at home here. Its slight sweetness balanced the sour lime and the heat. Red Boat made it sharper and more intense, which I liked less on a plain egg. For that condiment, the Thai-style bottle is the one I reach for.

The pattern in raw applications is that Red Boat gives you a cleaner canvas and the Thai-style bottle gives you something slightly rounder and pre-sweetened. Which one is better depends entirely on whether you want to add the sweetness yourself.

Cooked Dishes: The Gap Closes

I made two small batches of chicken wings with fish sauce in the marinade and tasted them side by side. Honestly, the difference mostly disappeared once the sugar caramelized and the garlic browned. If someone served me one without telling me which bottle was which, I would not have guessed.

That makes sense once you think about what heat does. The volatile aromatic compounds that distinguish the bottles (the caramel sweetness in the Thai, the briny depth of the Vietnamese) largely evaporate under high heat. What remains is amino acids and salt. Both bottles contribute plenty of those. The Thai-style one's added sugar also helps browning, but you can compensate with a pinch of sugar in the marinade when using Red Boat.

Which One to Buy

I keep both, and I did not expect to say that after doing this comparison. The biggest surprise was how little the two bottles differed once they were cooked. Paying more for fish sauce makes sense when you are using it raw, in dips and dressings, drizzled over rice, and not much sense when it goes into a hot pan with five other ingredients.

My current setup: Red Boat 40°N stays near the cutting board for anything that goes to the table raw. A Thai-style bottle (I use Tiparos or Thai Kitchen depending on what the store has) lives near the stove. Neither one is a backup for the other. They are doing different jobs.

If you only want one bottle and you cook more than you dip, get a Thai-style sauce and spend the savings on something else. If you make a lot of Vietnamese-style dipping sauces or salads, Red Boat will change how those taste. If you do both, you now have my excuse for keeping two bottles on the shelf.