The short answer to the headline question is, "Yes!" Even if you're teaching students online in an environment with more than one student, your students can have the interaction they need to improve their English language skills.
So how can you, as a teacher, structure a lesson in an online lesson where they can have meaningful communication? How can they negotiate meaning with other students so that they feel that they are flexing and improving their language skills?
The key is skillful coordination of the online classroom. Just as in a traditional classroom you pair students of similar or different proficiency levels depending on your teaching objectives for the lesson, you put students in small groups or pairs to work on a problem that requires them to use language to solve a certain problem.
If your online classroom offers a microphone feature for your students to use, learn to utilize it skillfully. In particular, turn off the microphones of students who are not working together. For instance, you might say, "John, ask Mary what her favorite sport is," or "John and Mary, look at the role play situation on the screen. John, you will play the part of the customer, and, Mary, you will be the manager. Work together to act out the situation and solve the customer's problem."
Being able to turn the microphone on and off is also important if you have a student who is dominating the conversation in a small class with about four students. Enable students to chat with you and each other through the chat feature of the class if students feel the need to communicate. You can simply tell a rather chatty student, "Thank you for your contribution!" and then open up the floor to other students.
Some online classrooms offer the opportunity for small breakout groups to work together on a particular task. You, as the teacher, can assign students to a particular breakout room and then check in with them to see how the conversations are going and to answer questions students may have.
Small group and paired interaction is important for students to develop their speaking and listening skills in English. Some students will feel that online classes in which they are not working one-on-one with a teacher directly will limit their opportunities to practice. However, the opposite is true! You can skillfully guide your students and help them to practice English in an online environment just as you would in a traditional classroom.