In Thai superstition, Wednesday is traditionally considered an unlucky day for cutting hair. The belief is especially associated with barbershops being closed on Wednesdays, although modern businesses do not all follow the custom.
The practice is part of a wider Thai system of auspicious and inauspicious days. Historical royal customs helped reinforce the idea that Wednesday was unsuitable for certain grooming activities, and ordinary people adopted related beliefs in different regions and families.
A common mistake is to treat this as a nationwide legal rule or a universal religious command. It is a folk belief, and many Thai people today choose haircut days according to convenience, salon schedules, or personal preference.
Wednesday has other associations in Thai culture as well. Traditional astrology connects days of the week with colors and planetary influences, and these associations can affect clothing, ceremonies, and naming customs. The haircut taboo is therefore best understood as one part of a larger calendar of auspicious timing.