Résumé
An elderly Thai widow with progressive dementia was transferred to Siriraj Hospital for properly continued supportive treatment. Due to the course of the disease, she lacked the ability to make any valid decision related to giving consent to medical treatment and to manage her own affairs. Giving medical consent was a critical issue confronting the treating physician whereas the patient\'s relatives might face with the issue of administering her personal affairs and property. In order to establish the patient's lawful substitute decision maker and administration for the patient's best interest, a declaration of the patient\'s incompetency and the appointment of suitable guardian were needed. The legal proceedings would inevitably be undertaken by filing a petition to the court. This would also have profound implications for the patient's rights and the physician's roles under the justice system.