China’s market size is much bigger even accounting for the fact that it’s more of a potential market size than an actual one (1.4 billion population for China versus 66 million population for your example of Thailand.... a 20x difference so that should answer your question about why not Thailand.)

That makes makes western companies do remarkable things in China. Not just partnering, but also opening branches in China and training up local staff with the latest techniques. Before long the leading edge technology is being developed in China, not elsewhere. This isn’t a made up scenario; it’s what has been happening for a couple of decades and now it’s getting pretty hard to ignore.

Tim Cook (Apple) said: “The U.S., over time, began to stop having as many vocational kind of skills,” Cook explained. “I mean, you can take every tool and die maker in the United States and probably put them in a room that we’re currently sitting in. In China, you would have to have multiple football fields.”

So the skills move there, the techniques move there, and pretty soon it should no longer be surprising that they also have the ability to make stuff well there.