What is "deksil"

Deksil (เด็กซิ่ว in Thai) means "Fossil Student" or "The Exam Re-Taker of the University Admission" , They are Students who graduated from high school but decided not to study in University.Instead, They spend a whole year to study at home or at Cram school for the university entrance exam for the better scores and better chance to get into the top universities like Chulalongkorn University, Thammasart University, Kasetsart University, Mahidol University, King Mongkut's University of Technology Thonburi