ผีเสื้อ

Etymology
From 🇰🇲.

As for the second sense, the insects got their name due to the old belief that they embody ancestral or tutelar spirits.

As for the third sense, the fish got their name probably due to their appearance or colours that look like butterflies.

Noun

 * 1) (classifier ตน) tutelar spirit.
 * 2)  (classifier ตัว) butterfly: insect of the order.
 * 3)  (classifier ตัว) butterflyfish: fish of the family, except , Heniochus spp.