Overview
A handful of aromatics carry most of the flavor identity across Thai cooking, and several of them resemble more familiar ingredients closely enough to cause real confusion at the store. Galangal looks like ginger. Makrut lime leaves get mistaken for a lime-zest substitute. Holy basil is often shelved or sold near sweet or Thai basil, despite tasting quite different once cooked.
This guide covers how to identify, choose, and store the aromatics that show up most often in Thai recipes, and it's honest about where substitution is a genuine compromise rather than a like-for-like swap. Getting the identification right matters more here than in many cuisines, because these ingredients aren't interchangeable with their closest lookalikes.
Regional cooking styles across Thailand use these aromatics somewhat differently -- a northern curry paste and a central-Thai curry paste may lean on different ratios of the same base ingredients -- so treat the descriptions below as general orientation rather than a single fixed standard for how any one aromatic must be used.
Lemongrass and Galangal
Lemongrass is a tall, fibrous stalk with a pale, dense base that tapers into tough green leaves you generally don't eat. The usable part is the bottom four to six inches, which gets bruised, sliced thin, or pounded into paste. Fresh stalks should feel firm and smell sharply citrusy at the cut end; woody, dried-out stalks have lost much of that aromatic oil. Frozen chopped lemongrass is a reasonable stand-in when fresh isn't available -- it softens on thawing, which makes it better suited to pounding into a paste than to fine slicing for garnish.
Galangal is not ginger. They're both knobby rhizomes with tan skin, which is where the confusion comes from, but galangal has a firmer, denser flesh, a sharper and more citrus-forward aroma, and a mild numbing quality that fresh ginger doesn't have. Cooked into a soup like tom kha, galangal contributes a distinct sharpness that ginger simply doesn't replicate -- substituting ginger changes the dish's character rather than approximating it. If you can't find fresh galangal, dried slices or frozen galangal are closer substitutes than ginger, though dried galangal is noticeably milder than fresh and works best rehydrated or pounded rather than used as-is.
When shopping for either aromatic fresh, look for firm, heavy stalks or roots without soft spots or shriveling. Lemongrass that bends easily near the base rather than snapping has likely dried out past its prime, and galangal with a wrinkled, papery skin has usually lost much of its moisture and aromatic punch along with it.
Makrut Lime Leaves
Makrut lime leaves come from a citrus tree and have a distinctive double-lobed, hourglass shape that makes them easy to identify once you've seen one. They're used whole or torn into curries and soups, or sliced into fine ribbons as a garnish for salads.
Makrut lime leaves are not the same as lime zest, even though both come from citrus and share some aromatic overlap. The leaf's aroma is more floral and complex than plain lime zest, and it releases slowly during cooking rather than delivering an immediate citrus hit. Zest can approximate a fraction of that brightness in a pinch, but it won't replicate the specific fragrance a recipe is written around -- treat it as an emergency substitution, not an equivalent ingredient.
Fresh leaves freeze well and hold their aroma much better frozen than dried. Dried leaves are shelf-stable and convenient, but they lose a meaningful amount of fragrance compared to fresh or frozen, so expect to use more of them, or expect a milder result, when that's the only form available.
A quick way to check quality at the store: fresh leaves should be glossy, deep green, and springy rather than limp, with a fragrance noticeable as soon as you tear or crush one slightly between your fingers. Leaves that look dull or feel leathery have usually been sitting for a while and will contribute less aroma to a finished dish even though they're technically still fresh, not dried.
Thai Basil and Holy Basil
Several basil varieties show up in Thai cooking, and mixing them up changes a dish noticeably. Thai basil (sometimes labeled Thai sweet basil) has purple stems and a mild anise or licorice note; it holds up reasonably well to heat and is the type most often used in curries and stir-fries where the herb is added toward the end of cooking.
Holy basil is not the same herb as Thai basil or sweet basil, despite frequently sitting near each other at the store. Holy basil has a sharper, more peppery, almost clove-like flavor and wilts and darkens quickly once cooked. It's the herb specifically associated with stir-fried dishes like pad kra pao, and swapping in Thai basil or Italian sweet basil produces a noticeably different, milder dish -- pleasant, but not the same flavor the recipe is built around.
If holy basil isn't available, Thai basil is the closer of the common substitutes, but expect a real difference rather than a subtle one. Italian sweet basil is the furthest departure of the three and should be treated as a last resort.
Cilantro Root and Dried Chiles
Cilantro root -- the pale, thin taproot attached beneath the leafy stems -- is a common curry-paste ingredient with a deeper, earthier flavor than the leaves. Most grocery store cilantro sold in the US has the roots trimmed off, so home cooks sometimes need to seek out bunches sold with roots intact, often at Asian grocers, or substitute the lower portion of the stems, which carries some of the same flavor at a lower intensity.
Dried Thai chiles (sometimes labeled bird's eye or prik kee noo) provide both heat and a different background flavor than fresh chiles once toasted or soaked. Heat level varies considerably by batch and by chile size -- smaller chiles in a bag tend to run hotter on average, but this isn't a reliable rule from bag to bag, so it's worth starting with less than a recipe calls for and adjusting upward.
Storage and Substitution
Fresh aromatics have the shortest shelf life and the strongest flavor. Lemongrass, galangal, and makrut lime leaves all freeze well, and freezing is generally the better preservation choice over drying if you want to retain aroma -- drying is more shelf-stable but sacrifices a noticeable amount of fragrance in exchange. Store frozen aromatics in a sealed bag or container and pull only what you need, since repeated thawing degrades texture and smell faster than a single freeze-thaw cycle.
As a general rule across this whole category: when a recipe calls for one of these ingredients and you only have a substitute on hand, it's worth thinking of the swap as a deliberate compromise rather than a hidden equivalent. Write it down, taste as you go, and adjust quantities -- these aromatics don't convert on a fixed ratio the way, say, table salt varieties often do.
Final Thoughts
Getting comfortable identifying these aromatics by sight and smell is one of the most useful skills for cooking Thai food at home, and it pays off well beyond any single recipe. Once you know what galangal, holy basil, and makrut lime leaves are actually supposed to look, smell, and taste like, shopping gets faster and substitutions become informed choices instead of guesses.
For buying guidance on dried, frozen, and fresh forms of these ingredients, visit the Thai Herbs and Spices hub, or see our broader Thai Cooking Ingredients hub for pantry-wide context.