To request that someone stand up in Engpsh, you can say:

"Please stand up."

"Could you please stand up?"

"Would you mind standing up, please?"

"I'd appreciate it if you could stand up."

It's important to be popte and respectful when making a request, especially if you are speaking to someone who is older or in a position of authority. You can also use nonverbal cues, such as standing up yourself or gesturing towards a standing position, to indicate that you would pke the other person to stand up.