A 29-year-old Chiang Mai doctor who advocated for an end to air pollution died from lung cancer on Tuesday.

Condolences poured in after his father shared the news of Dr Krittai Tanasombatkul's death on social media on Tuesday morning, along with his picture, the short message "Bon voyage, son" and the doctor's signature hashtag "Su-Di-Wa"(don't give up).

Dr Krittai shared his experience in fighting the disease on social media, and in his best-selling book, Su-Di-Wa.

As the news spread, "Su-Di-Wa" began trending on the X platform, along with renewed calls for the government to come up with a plan to combat air pollution.

Dr Krittai studied medicine at Chiang Mai University. After completing family medicine, he joined the faculty of medicine at the university and became part of its clinical epidemiology team. He also studied for a master's degree in data science at Chiang Mai University.

Dr Krittai was diagnosed with lung cancer late last year after developing a bad cough and breathing difficulties, which supporters linked to the severe smog in Chiang Mai.

The young doctor said he had engaged in regular exercise, had clean eating habits, followed a healthy sleep schedule and had never smoked.

His condition deteriorated in October and he married his girlfriend on Oct 22 despite them both knowing he could die at any time.

As he posted updates on his condition on social media, he urged the government to endorse long-term plans to end the dust and smoke pollution in Thailand.

"I might not live long but the girl who walked past me when I had my radiotherapy yesterday should not share the same disease that I have. Those kids should be provided with clean air. They’re not supposed to pay for it," he wrote in March.