"The Chinese Embassy in Bangkok lashed out at those who have bad-mouthed the Sinovac vaccine and Chinese goodwill towards Thailand".
That says it all, read between the lines. China does not like people/countries talking bad about their country and if they could rule the world, they would silence those forever, example Hong Kong, soon, Taiwan. Since the falling-out between China and Trump, China has been increasingly sensitive about people/countries disparaging China; they fight/talk-back like a child would.
"Goodwill"? China has a budget for Cambodia, Myanmar, and Thailand (and others) that monies goes into somebody's budget. Its not a fact but you can see by the actions of leaders from what China craves, power. Sinovac was the first and largest supplier to Thailand, why? Was it goodwill or was somebody persuaded to purchase huge quantities of Sinovac, we will never know.
It's a proven fact that Sinovac is substandard and with the upper-hand of the communist party, they will lie to the people and tell them otherwise. With their talk, who can trust China anymore. If China/China-Embassy doesn't like what I say, you will hear another child-like reply (talk back).
Don't get me wrong, I like China, the country, not the politics. But, since the falling-out with Trump, most Americans/westerners have been detained in China during the foreigner's vacation which makes anybody's vacation a nightmare, avoid traveling to China until China becomes more sensible.
China has a paradigm shift lately, self-sufficient and isolated except with countries connected to them and countries which have mineral deposits China craves. Watch-out other countries, China is here and present and if Thailand mis-behaves badly, China can close-down the south-China seas and nobody will be able to import or export. Yea, make them mad and see what you get, remember, they act like a child. Evidence, Myanmar and the bullet train fiasco.