function changeLang(lang){
      var thisurl=document.location.href;
      var pos=thisurl.indexOf("front");
      if(pos==-1) return;
//     var lang=thisurl.substring(pos+5,pos+7);
      if(lang=="en") lang="th";
     else lang="en";
      var newurl=thisurl.replace(thisurl.substring(pos,pos+8),"front_" + lang);
      window.location.href=newurl;
 }