According to the source, 95% of Thai TV dramas and series are made from popular novels written by talented authors. When producers or channels interested in the novels, they will buy the copyright of the novels before producing them as TV dramas.
After that, the producers will give those novels to the screenwriters to write the script for producing TV dramas.
The novels by a famous author Kingchat were made as TV dramas a lot including Buang Hong (James Jirayu and Kimmy Kimberley), Soot Sanaeha (Ken Theeradeth and Anne Thongprasom), Pohn Prom Onlaweng (Boy Pakorn and Bella Ranee), Khae Roi Rak (Ohm Atshar and Rita Sririta), Duang Jai Pisut (Son Yuke and Yam Matira), and many others.
For TV Series that was made from the popular novels including Sotus The Series, Ugly Duckling, Make It Right The Series, Lovey Dovey, U-Prince Series, and many others.