Ko Yao Yai is a relatively safe destination for solo female travelers. Visitors generally experience a welcoming and friendly environment. It's a tranquil and conservative island with very low crime rate. However, like any other travel destination, it's always important to stay vigilant, and keep personal belongings secure. Locals are friendly and respectful, but it's advisable to dress modestly respecting local customs. Avoid deserted areas at night and always let someone know your plans.