laugh
咍 centers on the act of laughing, often with a sense of amusement or mirth.
咍 combines 口 (mouth) with 台, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound related to vocal expression.
A mouth 口 making the sound 台 (like a platform for laughter) — imagine a mouth laughing heartily on a stage.
For カイ, picture a laughing mouth that sounds like a high-pitched 'kai!' — a cheerful exclamation that matches the reading.