EDIT Usage Considered to be a simple vocalic -ำ [am]

This is a spacing combining character that appears to the right of a base character.

This character interacts typographically with the preceding consonant, but is not classed as a combining character. The character must be kerned so that the small circle appears over the top right shoulder of the preceding consonant, and although the order should be consonant+tone mark+am, the tone mark should still appear above the circle, eg น้ำส้มคั้น [námsɔ̂mkán].

 richardishida