You say that he is understands all of the verbal commands given in English, which would mean to me that he understands the basic English language. Most of the time it sounds like he only talks when he is ready to. This could be considered that child's silent period, were he just wants to take in that language and not try to use it unless required to. Unless you need him to talk during class I would not think that you should be worried and let him learn like this as is becuase he might just start talknig on his own. If it is truely important to get him to talk in class, pair him up a with a buddy or make more group work so he will interact with more people and more likey be requreied or willing to talk.

Try and find something the student is interested in. Observe characters on his clothes, backpack, shoes, folders, supplies, etc. Generally if you can find something a child is interested in the student will speak more often.

This is a very common concern among teachers. You are trying your best but the student is not talking to you. I agree with the first post. The silent period is part of the learning process. ESOL students need to have a comfort zone. I will recommend praising his progress and possible rewards. By doing that you will be creating a "different" kind of comfort zone where he/she feels accepted. Pairing him with a buddy is a great idea too.

Maybe if you have time can one on one, repetition, posters in the wall and let the students work with other students for activity. Hope this will help.

There are some students that are quite in nature. pair him with a body, use a lot of group work activities, it will probably take some time before he stars talking but I am sure can build confidence around others.

This is the process, I would use visuals until he feels comfortable to start expressing his emotions and needs verbally.

I think that one possible solution could be making the teaching lessons related to something that he likes maybe a specific sport or cars.