title: Tesseract SetVariable tessedit_char_whitelist in another language
body: <p>Tesseract setVariable whitelist works ok for english language for example i use this to recognize only digits and letters from image (excluding special characters &amp;*^%! etc)</p>
  
  <pre><code>_ocr.SetVariable("tessedit_char_whitelist",
  "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
  </code></pre>
  
  <p>But i can't do the same thing for Thai language</p>
  
  <pre><code>_ocr.SetVariable("tessedit_char_whitelist","0123456789กขคงจฉ");
  </code></pre>
  
  <p>Is there a different principle? Because this does not work. Instead of all determined characters I receive only digits in output, tesseract ignores all Thai letters which I put into the whitelist.</p>
  
  <p>How can I pass this variable correctly?</p>