Tun has worked in Burma's Department of Meteorology and Hydrology since 1965 when he was 17 years old in 1965. He then served as Deputy-Director in the Ministry of Meteorology and Hydrology until 2003 when he was promoted to Director General of Department of Meteorology and Hydrology. One of the most notable occurrences during his appointment was
Cyclone Nargis, the worst natural disaster to hit Myanmar in recorded history. Despite the high number of casualties and devastation, he was commended after initial criticism for his prediction and speedy warning of the Cyclone especially considering the limited resources and political bureaucracy of Burma at the time. After 44 years in total at the DMH, he retired in 2009. After his retirement, he actively engaged in raising awareness about the need to adequately prepare for natural disasters. On December 10–11, 2009, Lwin presented his 30-page paper at a seminar hosted by the
International Centre for Water Hazard (ICHARM) in
Tsukuba,
Japan, stressing the importance of awareness of storms, tsunamis and flooding in delta regions and potential natural disaster preparedness strategies in the region. In October 2010 he spoke to the Burmese media about the expected path of
Cyclone Giri. In 2011, he founded Tun Lwin Foundation. On the environmental conservation front, he was seriously opposed to the
Myitsone Dam project slated for construction at the confluence of two rivers that gives rise to the
Irrawaddy River. Though his health was already in decline, he showed up at an anti-dam event in
Yangon in 2017 to deliver a strong statement, insisting, "I cannot accept any dam project on the Irrawaddy River". In 2017, he received the 7Day Heroes award for his non-profit work for the country in his field of meteorology, weather and climate. ==Personal life==