A look at how Thai curry took shape long before chillies arrived, and what genuinely separates the red paste from the green.
Thai curry's story begins well before the dish resembled anything served today. Long before chillies reached Southeast Asia, Thai cooks were already building thick, aromatic pastes from lemongrass, galangal and shallots, pounded together in a stone mortar to flavour meat and fish, a style historians trace back to the Sukhothai era (13th–15th centuries) and the Ayutthaya kingdom that followed. Portuguese traders are widely credited with introducing chilli peppers to the region during the sixteenth and seventeenth centuries, part of the wider exchange of New World crops that reached Southeast Asia in the wake of Portugal's 1511 conquest of Malacca. Before that point, heat in Thai cooking came from black pepper, not chilli.
Indian and Persian traders passing through Ayutthaya's ports also left their mark on Thai cooking, particularly during the cosmopolitan reign of King Narai (1656–1688), when the kingdom's trade links across the Indian Ocean reached their peak. They contributed the word "gaeng" alongside a grounding in paste-based, spice-forward cookery, though the resulting dish diverged sharply from anything found on the subcontinent. Thai gaeng is built on fresh aromatics pounded to a paste rather than dry-roasted whole spices, and it typically carries far more liquid, closer to a soup than a stew. By the time chillies had settled into the Thai pantry, red and green pastes had each found their own identity, distinguished chiefly by whether the chilli used was dried or fresh.
In Thai households, curry paste making has traditionally marked out a skilled cook. Convenience is widely credited with reshaping this practice from the 1960s onward, as Thailand's rapid urbanisation and post-war economic growth led more households to buy ready-made paste from the market rather than pound their own by hand. Fresh curry paste is still sold daily at markets across Thailand, prepared each morning by vendors whose blend is often a closely guarded point of pride.
Curry sits at the centre of the Thai way of eating together. Rather than a single main course, a Thai meal is usually built from several dishes shared across the table, with a curry providing the central savoury, often liquid element, balanced against a dry stir-fry, a salad and plain rice. Eating this way makes curry as much a social gesture as a flavour choice, since its presence signals a proper, complete meal rather than a quick one.
The difference between a Thai red curry and a Thai green curry begins with the chilli. Red curry paste is built from dried red chillies, soaked and blended until smooth, which gives the finished paste its deep, brick-red colour and a rounder, slightly smokier heat. Green curry paste instead uses fresh green chillies, most often the small, fierce bird's eye variety, blended raw. The result is a paste that tends to taste sharper and grassier, with a heat that can register as more immediate even when the overall spice level is similar.
Beyond the chilli, the two pastes share much of the same backbone: lemongrass, galangal, garlic, shallots and kaffir lime, usually alongside shrimp paste or dried shrimp for savoury depth. Green curry paste typically carries a heavier dose of fresh coriander root and Thai basil worked directly into the blend, contributing to its brighter, more herbaceous finish. Red curry, leaning on dried chilli rather than fresh, tends to read as the deeper, more robust of the two.
Neither curry is inherently hotter than the other on paper, since heat depends on the chilli quantity and variety used in a given batch, but green curry has built something of a reputation in the West for packing a sharper punch, largely because raw bird's eye chillies carry a more immediate heat than their dried counterparts.
Central Thai cuisine, particularly the refined cooking associated with the royal court in Bangkok, is usually credited with establishing the red and green curry pairings most familiar today, but curry culture varies significantly outside the capital. In the north, curries tend to use less coconut milk and lean on a thinner, more savoury broth. In the south, where Indian and Malay trading influence runs deeper, curries often carry a stronger showing of turmeric and are noticeably spicier, reflecting closer historical ties to the wider spice trade routes of the Indian Ocean.
Thai curry's international spread accelerated from the 1960s onward, as Thai communities established restaurants first in the United States and later across Europe, with the UK's Thai restaurant scene expanding rapidly through the 1980s and 1990s. Restaurants adapting the dish for new audiences abroad often increased the proportion of coconut milk relative to what is typical in Thailand itself, producing a richer, creamier curry than the thinner, more broth-like versions eaten at home. This adapted style has, in turn, become many people's first and most familiar version of Thai curry, even as the leaner, more herb-forward home-style version remains the everyday standard within Thailand.
The core difference comes down to the chilli. Red curry paste uses dried red chillies, giving it a deeper colour and rounder heat, while green curry paste uses fresh green chillies, usually bird's eye, blended raw for a sharper, grassier result. Both share the same base of lemongrass, galangal, garlic and shallots.
Not necessarily. Heat depends on the quantity and variety of chilli used in a specific batch of paste, not the colour itself. Green curry has a reputation for feeling hotter because raw bird's eye chillies carry a sharper, more immediate heat than dried chillies do, but a heavily chillied red curry can easily out-spice a mild green one.
Gaeng is the Thai word most often translated as curry, though it covers a broader category of paste-based, liquid dishes than the English word suggests. Unlike curries built around dry-roasted spice blends, a Thai gaeng starts from a wet paste of pounded fresh aromatics.
Many restaurants outside Thailand increase the ratio of coconut milk to make the dish richer and more approachable for audiences less familiar with the cuisine. In Thailand, home-style curry is often thinner and more broth-like, letting the herbal and chilli notes come through more directly.