Mae Sai, is generally a safe destination for solo female travelers. Crime rates are comparatively lower than many other regions and locals are often friendly towards tourists. However, as it is a border town, there may be some instances of petty crime like pickpocketing. Always remain vigilant, especially in crowded places. Of course, standard travel precautions should always be applied - watch your belongings, avoid isolated areas after dark, and stay in touch with someone about your whereabouts.