the wrong language.">
<style>
#wrap, #ref {
  font-size: 2em;
  border: solid orange;
  margin: 5px;
  width: 30ch;
}
@supports (word-boundary-detection: auto(th)) {
  #test {
    word-boundary-detection: manual;
  }
}
#test {
  width: 0;
  word-boundary-detection: auto(th);
}
</style>

<p>Test passes if the two boxes below are <em>different</em>.

<div id=wrap lang=ja>
  <div id=test>กรุงเทพคือสวยงาม</div>
</div>
<div id=ref lang=ja>กรุงเทพคือสวยง