"Nha", "nhá", "nhé" is a part of a Vietnamese sentence type called "câu cầu khiến". We use "câu cầu khiến" when you want to ask/convince somebody to do something. According to the correct grammar, we need to use the exclamation mark at the end of the sentence. However, people often ignore it in informal speeches. I am not sure whether there is any official translation for these kinds of words. In my opinion, it can be translated like "ok" or "please". Let's go through some examples:
Mẹ mua đôi giày này cho con nhé! - (Mom) please buy me this pair of shoes!
Bạn chờ mình chút nha! - Wait (for me) a moment, please!
Chiều mai đi bơi với tao nhá! - Go swimming with me, ok?
"Nhá" is more friendly/informal than the others.
"Nhỉ" is often used at the end of sentences:
- As a tag question: "isn't it?", "doesn't it?", etc,. And mostly you know that the listeners think the same/agree with you. So in this kind of questions, it doesn't really need a response.
Bài hát hay quá, anh nhỉ? - The song is too/so beautiful, isn't it?
- As "huh?" in English.
Sao trông cô ấy buồn thế nhỉ? - Why she looks so sad, huh?
I hope this is helpful to you.