Nearly every Thai recipe begins with a paste. While it is possible to buy ready-made Thai pastes (such as red, yellow, and green curry), these packaged spice mixes will not give you the same flavor and aroma—not to mention nutrients—as a paste made from scratch.
In the Thai kitchen, pastes were traditionally made using whole spices and herbs (some fresh, others dried) pounded together with a pestle & mortar. While many Thai chefs still prefer to use this method, a food processor is a convenient and adequate substitute.
Most Thai pastes start with shallots (or onions), garlic, and green or red chilies. Added to this may be a variety of other spices and herbs, including dried or fresh coriander, Thai chili powder, galangal, green peppercorns, lemongrass, and turmeric. Kaffir lime leaves are also a common ingredient, lending a uniquely Thai flavor to pastes or simmering dishes.
Lemongrass is used in various ways in Thai cooking. For some dishes, it is chopped and pounded, other times it is simply cut into long pieces and “bruised” (bent and kneaded or even lightly cut in several places) to release the scent and flavor for soups and curries.
Galangal is a relative of ginger, as is fresh turmeric. If you can't find galangal (it's usually purchased frozen at Asian food stores in North America), you can substitute ginger. These roots (actually rhizomes) add valuable nutrients and depth of flavor to many Thai dishes.
Finally, no Thai kitchen would be complete without a good supply of fresh basil. Thais make use of several types of basil in their cooking, included sweet basil, and Thai holy basil.
See our Glossary of Thai Ingredients for more information on these herbs and spices, along with pictures to help you recognize them at your local Asian store or market. Or see my How to Shop for Thai Ingredients at an Asian Food Store or Market. For Thai recipes, see links below.