ExoPlayer and start / pause / seekTo commands

The official example of the PlayerControl in the ExoPlayer source code do exactly what you asked:

public class PlayerControl implements MediaPlayerControl {

  private final ExoPlayer exoPlayer;

  public PlayerControl(ExoPlayer exoPlayer) {
    this.exoPlayer = exoPlayer;
  }

  @Override
  public boolean canPause() {
    return true;
  }

  @Override
  public boolean canSeekBackward() {
    return true;
  }

  @Override
  public boolean canSeekForward() {
    return true;
  }

  @Override
  public int getAudioSessionId() {
    throw new UnsupportedOperationException();
  }

  @Override
  public int getBufferPercentage() {
    return exoPlayer.getBufferedPercentage();
  }

  @Override
  public int getCurrentPosition() {
    return exoPlayer.getDuration() == ExoPlayer.UNKNOWN_TIME ? 0
        : (int) exoPlayer.getCurrentPosition();
  }

  @Override
  public int getDuration() {
    return exoPlayer.getDuration() == ExoPlayer.UNKNOWN_TIME ? 0
        : (int) exoPlayer.getDuration();
  }

  @Override
  public boolean isPlaying() {
    return exoPlayer.getPlayWhenReady();
  }

  @Override
  public void start() {
    exoPlayer.setPlayWhenReady(true);
  }

  @Override
  public void pause() {
    exoPlayer.setPlayWhenReady(false);
  }

  @Override
  public void seekTo(int timeMillis) {
    long seekPosition = exoPlayer.getDuration() == ExoPlayer.UNKNOWN_TIME ? 0
        : Math.min(Math.max(0, timeMillis), getDuration());
    exoPlayer.seekTo(seekPosition);
  }

}

If you are experiencing strange behaviors during the seek operation, it may be due to you particular stream/file type. I can suggest you to take a look at the base implementation of the ExoPlayer and, eventually, report any issue on Github.