Women should avoid taxis when alone at night. Self-driving not recommended. Parking is difficult. On trains to Malaysia, guard against pickpockets. Avoid buses, especially overnight trips.
Boats often are crowded and dangerous.
Watch for petty theft in Patpong and Soi Cowboy entertainment districts and in tourist areas. Purse-snatchers on motorcycles are common. Avoid city's canal areas after dark. Keep valuables in hotel safe, including passport. Carry photocopy of passport at all times.