Thai Long Beans vs. Green Beans: How to Identify Them and When to Swap

The short answer

The long beans used in Thai cooking are yard-long beans, also called snake beans or yardlong beans. Botanically they are Vigna unguiculata, Sesquipedalis Group (sometimes listed as Vigna unguiculata subsp. sesquipedalis). The part you cook is the succulent immature pod. Ordinary American green beans, also called snap or string beans, are a different species, Phaseolus vulgaris. Both belong to the legume family, Fabaceae, but they are not the same plant. In at least two documented Thai recipes, a red curry stir-fry and a pounded bean salad, the recipe authors allow green beans in place of long beans.

How to recognize Thai long beans

The common names describe the ingredient. "Yard-long" and "snake" refer to the pod's long, slender shape. Thai and Southeast Asian recipes written in English usually call them long beans or yardlong beans. Some recipe titles use "green beans" while still accepting either bean, so check the ingredient list rather than relying on the dish name.

• Yard-long bean (long bean, snake bean): Vigna unguiculata, Sesquipedalis Group. The plant is an annual climbing vine, and the vegetable is the immature, succulent pod.
• Green bean (snap bean, string bean): Phaseolus vulgaris. The pods are harvested while young and tender.
• Shared trait: both are legumes in the family Fabaceae. Being in the same family does not mean they behave the same way in every dish.

If a label or menu gives a botanical name, that settles the question. Vigna points to the long bean; Phaseolus points to the common green bean.

Choosing between long beans and green beans in Thai dishes

The best way to cook long beans depends on the dish. Two well-documented Thai preparations treat the beans very differently. One briefly blanches them and then stir-fries them with curry paste. The other leaves them raw and bruises them in a mortar. In both recipes the author accepts green beans as an alternative. Each recipe's own approval is what justifies the swap, not a general rule that the two beans always behave alike.

Feature	Red curry stir-fry (Pad Ped Tou Kag)	Pounded long bean salad (som tum tua)
Bean named in recipe	Green or long beans	Yardlong beans
Cut size	About 5 cm pieces	About one-inch pieces
Preliminary step	Boil 30 seconds, then drain	None; beans stay raw
Main technique	Stir-fry in a wok with red curry paste	Gently pound in a mortar until the beans start to split
Key seasonings	Red curry paste, fish sauce, sugar, a little boiling water	Garlic, dried chilies, palm sugar, fish sauce, tamarind, lime, tomato
Author-approved alternative	Either bean listed from the start	Green beans permitted

In a stir-fry: Sallie Morris's Pad Ped Tou Kag

Sallie Morris's recipe, published in English as Thai spicy green beans and reproduced with permission by the blog Kavey Eats, calls for green or long beans trimmed into roughly 5 cm lengths. The beans get a 30-second boil and are drained. Red curry paste is fried in oil in a wok over moderate heat until its color deepens and it becomes fragrant. The beans are then stir-fried until tender. Fish sauce, sugar and a small amount of boiling water go in last, the pan is brought quickly to a boil, and the dish is served immediately.

Either bean works here because the recipe was written to accept both. The brief blanch and the hot, fast finish are the parts to keep, whichever bean you buy.

In a pounded salad: Praew's som tum tua

Som tum is the Thai family of pounded salads best known in its green papaya form. Tua means beans, so som tum tua is the bean version. In Praew's version, published on Hungry in Thailand, yardlong beans are cut into about one-inch pieces. Garlic and dried chilies are crushed first. The beans are then pounded gently until they begin to split, which lets them absorb the dressing. Fish sauce, optional fermented fish sauce, tamarind paste and palm sugar are worked in until the sugar dissolves. Lime juice, a piece of the lime peel and small tomatoes are folded in gently just before serving.

Praew lists green beans as an acceptable alternative for this salad. Because the beans are never cooked, the pounding step does all the work. Bruise them just enough to split, not to mash, whichever bean you use.

Practical takeaway

Use long beans when you want the ingredient these Thai recipes name first. If you can only find green beans, both of these dishes explicitly allow them. Keep each recipe's own sequence: blanch then stir-fry for the curry dish, and pound raw for the salad. Don't assume the swap carries over to every Thai recipe. Check whether the cook you're following offers it.