SP.File file = clientContext.Web.GetFileByServerRelativeUrl(SpCommonCOM.toRelative(path));
clientContext.ExecuteQuery();

FileSaveBinaryInformation fsi = new FileSaveBinaryInformation();
byte[] raw = new byte[docLen];
doc.Read(raw, 0, docLen);
fsi.Content = raw;

file.SaveBinary(fsi);

if (revOpt.Equals("1"))
    file.CheckIn(comment, CheckinType.MajorCheckIn);
if (revOpt.Equals("2"))
    file.CheckIn(comment, CheckinType.MinorCheckIn);
if (revOpt.Equals("3"))
    file.CheckIn(comment, CheckinType.OverwriteCheckIn);
clientContext.ExecuteQuery();