Social media anger from Chinese nationalists over a Thai internet model's comments on the coronavirus has set off a storm, uniting pro-democracy campaigners against pro-Beijing cyberwarriors, with insults and mocking memes flying.

The quarrel, which has seen Southeast Asian internet users join forces with those in Taiwan and Hong Kong, has highlighted old tensions between China and its smaller neighbors, with those fanned by the emergence of the new coronavirus.

Political analysts and activists said the online row, which started at the weekend, was unique in volume and regional spread at a time when ever more of life has been forced online.

"This is the first transnational geopolitical Twitter war Thais have engaged in," said Prajak Kongkirati of Bangkok's Thammasat University.

"We see people questioning China's actions and influence. … The celebrity issue is the tip of the iceberg."

Related Twitter hashtags generated more than two million tweets and trended globally. A fan page for the main hashtag, #Nnevvy, has more than 63,000 Facebook followers.

"Nnevvy" is the social media moniker of internet model Weeraya Sukaram, and the dispute began after she was accused of sharing a Thai Twitter message questioning whether the coronavirus originated in a Chinese laboratory.

Furious Chinese netizens then said she had once appeared to suggest, in a post on Instagram, that Taiwan was not part of China. Beijing says the self-ruled island is an indivisible part of its territory.

Weeraya did not respond to requests for comment and neither of the messages was visible on her accounts.

Further fuelling the fire, Chinese accounts then accused Weeraya's boyfriend, Vachirawit Chivaaree, of having once liked a post that identified Hong Kong as a country — again a no-no for Beijing.

Despite his apology, they called for a boycott of his hit TV show.

Related hashtags on Chinese microblogging platform Weibo resulted in more than 4.64 billion views and 1.44 million posts.

In the face of the pro-China barrage, support rallied for the Thai celebrities from anti-Beijing activists and politicians — including Hong Kong pro-democracy campaigner Joshua Wong and a Taiwan mayor.

Wong posted a photo watching Vachirawit's show and urged Hong Kong to "stand with our freedom-loving Thai friends".

"Perhaps we can build a new kind of pan-Asian solidarity that opposes all forms of authoritarianism!" he wrote.

Thai pro-democracy student activist Netiwit Chotiphatphaisal said he and Wong had been in touch and that Thais were uneasy over growing Chinese influence since a 2014 coup in Thailand, whose leader, Prayut Chan-ocha, won a disputed election last year.

"The hashtag provided an opportunity to speak up," Netiwit said.

Meanwhile, some users in the Philippines took on the hashtag to attack Chinese action in the disputed South China Sea.

China's foreign ministry pointed the finger at a plot to stir up trouble and said China and Thailand were working closely together, including on the coronavirus outbreak.

"Certain people use the opportunity to incite dispute on the internet, creating oppositions between public opinions, playing off China-Thailand relations, their plot shall not succeed," the ministry said in a response to questions.

Twitter is blocked in China and only accessible for those using virtual private networks or with official approval.

Social media consultancy Drone Emprit found that automated bot accounts were using the #Nnevvy hashtag but it did not say where they came from. Reuters found that several pro-China accounts had been created in the last few days and only contained comments on the dispute.

"While #Nnevvy started off as an intense overnight Twitter war between Thailand and China, it's now turned into meaningful diplomatic engagement with Hong Kong and Taiwan," said Tracy Beattie of the Australian Strategic Policy Institute.

Insults from Chinese nationalists against Thailand's government and king were laughed off by Thai campaigners who themselves attack the administration as undemocratic. The king has faced unprecedented online criticism recently despite a penalty of up to 15 years in jail for anyone insulting him.

Thailand's government was aware of the social media battle between Thai and Chinese accounts and it urged Thai internet users to express themselves within reason, said deputy government spokeswoman Ratchada Thanadirek.

Thai posters, using one well-known internet meme, labelled a menacing character as Chinese people trying to hurt Thai people's feelings by insulting their country. A nonchalant character was described as Thai people who have been insulting their country for years.

Meanwhile, Thai users mocked China for authoritarian rule and likened Chinese President Xi Jinping to Winnie the Pooh — a comparison that is banned in China.

"Thailand is poor, but China is Pooh," read one viral tweet.

On a lighter note, another meme celebrated Thailand, Hong Kong and Taiwan as a "Milk Tea Alliance" because of a shared fondness for the iced drink.