No hard and fast rule says that one should not wear a ring on their thumb. However, some potential issues can arise from wearing a ring on the thumb, mainly if the call is large or heavy.

Wearing a ring on the thumb can interfere with fine motor skills and hand movements, as the thumb is an important digit for gripping and manipulating objects. This can be particularly problematic if the ring is large or bulky, making it difficult to perform tasks requiring precision or skill.

It can also cause irritation or discomfort, mainly if the ring is too tight or loose. This can lead to skin irritation, soreness, blisters, or calluses.

It’s also seen as a fashion faux pas in some cultures or social settings. In some cultures, wearing a ring on the thumb is associated with specific meanings or symbolism that may not be appropriate for all occasions.

While there is no hard and fast rule against wearing a ring on the thumb, the potential drawbacks and social implications are worth considering.