Police have searched Lam Tin Park and a cemetery in Tseung Kwan O - two of Tsoi's favourite hangouts - but did not find him. There were reports that the student was seen up on Lion Rock. Police said they would consider carrying out a search there.
Tsoi is 1.73m tall and weighs about 58kg. He was last seen wearing a black hoodie, a red shirt, blue jeans, and black sneakers. He carried a black backpack. He had left a note on his computer saying he would run away from home.
He was reportedly facing academic and relationship problems. Police asked people with information about Tsoi to call Kowloon East missing persons unit at 2703 2335.