Salty, fermented fish sauce with fresh chilies (called nahm phrik pla raa) is the most important flavoring ingredient in Thai cooking. It is like salt to Americans and soy sauce to the Chinese.
Chili sauce or paste (called nahm phrik) is foundational to the Thai diet, and each region has its own version. A mortar and pestle is used to crush chilies together with such ingredients as garlic, shrimp paste, lime juice and fish sauce. It is used as a vegetable dipping sauce or eaten with rice.
Soups are paramout to Thai cuisine, perhaps because they allow the use of small amounts of various ingredients boiled in a pot to feed many people.
Copious use of fresh, rather than dried, herbs and spices, is the norm in Thailand.
Curry is essential to the diet, and usually is one of four types: green, red, yellow and massaman (which has Muslim roots).
The fork and spoon rule in Thailand. Chopsticks are not as common.