Chuang Chuang had been at the Chiang Mai zoo on loan from China since 2003.
The 19-year old bear was widely popular across Thailand, especially due to repeated efforts by the zoo to get him to mate with his female companion.
His unexplained death on Monday caused an uproar on Chinese social media, with many users accusing Thailand of not caring properly for the animal.
Giant pandas, which are native to China, usually live for 25 to 30 years in captivity. They were regarded as endangered but were reclassified as “vulnerable” by the International Union for Conservation of Nature, following an increase in numbers.
China loans animals to countries around the world as a way of strengthening diplomatic ties.
There’s extensive reporting in China about the animals’ lives overseas, and Chuang Chuang’s early death has received widespread coverage in state media.
According to Chinese news agency Xinhua, an investigation will be carried out to establish the cause of death, and experts from the China Conservation and Research Centre will travel to Chiang Mai to work with their Thai counterparts. bbc