BANGKOK, April 21 -- A viral video featuring a Thai tourism adviser's angry reaction to a Russian tourist's use of the Mandarin-language greeting "Ni hao" has sparked a heated debate across social media platforms, reigniting questions about racial sensitivity and cultural identity in Thailand.

The video shows Siranath Bhiromphakdee, known as Sai Scott, confronting a Russian man and his partner on a beach in Krabi province. The couple had been found on an island during an off-limits period after hiring a guide to take them there.

Upon learning that their visit violated regulations, the Russian man greeted Scott with "Ni hao," Mandarin for "Hello." Scott, visibly agitated, demanded that the tourists leave, warning that if the greeting was...