Seub Nakhasathien (Thai: ??? ??????????, pronounced [s?`?p? na?.k?á?.sà ?.t?ian],RTGS suep nakhasathian; 31 December 1948 – 1 September 1990) was a Thai conservationist, environmental activist, and scholar who is renowned for his effort to protect Cheow Lan Lake (Rajjaprabha Dam Reservoir), Thungyai Naresuan Wildlife Sanctuary, and Huai Kha Khaeng Wildlife Sanctuary.
Seub committed suicide to signify the importance of the environment and to preserve it.
According to the Bangkok Post, "The death of Seub Nakhasathien, a forest conservator who committed suicide in 1990,...helped transform the status of Thungyai Naresuan and the adjacent Huay Kha Kaeng Western Forest Complex into a sacrosanct site and inspired many youth to become forest patrol staff."