I used to work in the semi-conductor industry, and I would say well over 50% of our department was from outside the US (our company was based in Santa Clara California), many were from Asia. Since I was a software engineer, I would often interview people applying for programming jobs. It took me some time to develop an interviewing strategy, but what I eventually started doing was asking candidates to explain some well-known algorithms and also explain solutions to problems that they had come up with. Basically, ask pretty technical questions. The idea wasn't to make them uncomfortable or anything. You want to ask questions that they should reasonably know. And even if they don't know everything, they should be able to answer some of the questions. I've seen a lot resumes with tons of buzz words on them, but when you actually start to ask questions, some candidates seem to know very little.
In your case, you would also get them into a technical discussion in English, which I think would tell you a lot about how well they will interact if they get the job.
Here's kind of a funny story which isn't directly related but anyway …… We had this candidate from India who had the most insane resume that we'd ever seen. He had degrees from MIT, Stanford and Berkley. He was also a track star and had worked for the CIA. He was supposed to be an AI expert. This guy I didn't get to interview since I was still a tech at the time. He was hired instantly by the head of our department, and nobody really checked his credentials. Basically, he was a good talker that knew many buzz words and presented himself very well. After he was hired, he was given free rein to find projects.
At one point he came to me and said he had heard I programmed in assembly language, which was in fact my job at the time. When I said yes, he asked me “what's that like?". I was a bit surprised that he had never at all encountered it in his studies, so later I asked him what languages he knew? He said only LISP and he was very rusty, as all his work was theoretical. I was shocked and actually told him to his face “I don't believe it". I talked to a couple managers but they kind of blew me off, so I let it go. A few weeks later the head of the AI department met with him and got suspicious. Turns out all his degrees were in fact bogus, as well as everything else in his resume. I guess if you're going to lie, lie big! LOL! At least he got a fat paycheck for a few months.