Thanks for answer but i think this is not the problem. I change my code as this but it is not work.

 <rich:panel>
 <f:facet name="header">
 <h:outputText value="#{Bundle.TEXT_INSCRIP}"/>
 </f:facet>
 <div>
 <rich:message showSummary="true" showDetail="false" styleClass="errorMessage" for="registerForm"/>
 </div>
 <h:panelGrid cellpadding="3" width="500px" columns="3">
 <h:outputLabel styleClass="label" value="#{Bundle.NAME}"/>
 <h:inputText id="name" size="30" required="true" value="#{RegisterBackingBean.currentUser.nom}"/>
 <rich:message styleClass="errorMessage" for="name"/>

 <h:outputLabel styleClass="label" value="#{Bundle.SURNAME}"/>
 <h:inputText id="prenom" size="30" required="true" value="#{RegisterBackingBean.currentUser.prenom}"/>
 <rich:message styleClass="errorMessage" for="prenom"/>
 <h:outputLabel styleClass="label" value="#{Bundle.USERNAME}"/>
 <h:inputText id="username" size="30" required="true" value="#{RegisterBackingBean.currentUser.userName}"/>
 <rich:message styleClass="errorMessage" for="username"/>
 <h:outputLabel styleClass="label" value="#{Bundle.PASSWORD}"/>
 <h:inputSecret id="password" size="31" required="true" value="#{RegisterBackingBean.currentUser.password}"/>
 <rich:message styleClass="errorMessage" for="password"/>
 <h:outputLabel styleClass="label" value="#{Bundle.PASSWORD_CONFIRM}"/>
 <h:inputSecret binding="#{RegisterBackingBean.secondPassword}" id="passwordConfirm" size="31" required="true"/>
 <rich:message styleClass="errorMessage" for="passwordConfirm"/>
 <h:outputLabel styleClass="label" value="#{Bundle.EMAIL}"/>
 <h:inputText id="email" size="30" required="true" value="#{RegisterBackingBean.currentUser.email}">
 <f:validator validatorId="miwa.emailValidator"/>
 </h:inputText>
 <rich:message styleClass="errorMessage" for="email"/>
 <h:outputLabel styleClass="label" value="#{Bundle.EMAIL_CONFIRM}"/>
 <h:inputText binding="#{RegisterBackingBean.secondEmail}" id="emailConfirm" size="30" required="true">
 <f:validator validatorId="miwa.emailValidator"/>
 </h:inputText>
 <rich:message styleClass="errorMessage" for="emailConfirm"/>


 <h:outputLabel styleClass="label" value="#{Bundle.COUNTRY}"/>

 <h:selectOneMenu value="#{RegisterBackingBean.currentUser.paysidPays}" binding="#{RegisterBackingBean.paysMenu}" id="pays">
 <f:selectItems value="#{RegisterBackingBean.paysItems}"/>
 <f:converter converterId="paysConverter"/>
 <a4j:support event="onchange" reRender="regionLabel,region" action="#{RegisterBackingBean.paysListener}"/>
 </h:selectOneMenu>

 <h:outputLabel id="regionLabel" rendered="false" styleClass="label" value="#{Bundle.REGION}" binding="#{RegisterBackingBean.regionLabel}"/>

 <h:selectOneMenu id="region" immediate="true" rendered="false" binding="#{RegisterBackingBean.regionMenu}" value="#{RegisterBackingBean.currentUser.regionidRegion}">
 <f:selectItems value="#{RegisterBackingBean.regionItems}"/>
 <f:converter converterId="regionConverter"/>
 <a4j:support event="onchange" immediate="true" action="#{RegisterBackingBean.regionListener}"/>

 </h:selectOneMenu>

 <h:outputLabel id="departementLabel" binding="#{RegisterBackingBean.departementLabel}" rendered="false" styleClass="label" value="#{Bundle.DEPARTEMENT}"/>
 <h:selectOneMenu rendered="false" binding="#{RegisterBackingBean.departementMenu}" value="#{RegisterBackingBean.currentUser.departementidDepartement}" id="departement">
 <f:selectItems value="#{RegisterBackingBean.departementItem}"/>
 <f:converter converterId="departementConverter"/>
 </h:selectOneMenu>

 <h:commandButton action="#{RegisterBackingBean.registerUser}" value="#{Bundle.REGISTER}" />
 </h:panelGrid>
 </rich:panel>

 public String paysListener() {

 this.regionLabel.setRendered(false);
 this.regionMenu.setRendered(false);
 this.regionItems.clear();
 this.departementItem.clear();
 this.departementLabel.setRendered(false);
 this.departementMenu.setRendered(false);
 this.currentUser.setRegionidRegion(null);
 this.currentUser.setDepartementidDepartement(null);

 if (this.getPaysMenu().getSubmittedValue() != null) {
 Pays ps = paysFacade.findByname((String) this.getPaysMenu().getSubmittedValue());
 if (ps != null) {
 this.currentUser.setPaysidPays(ps);
 if (ps.getHasRegion()) {
 this.regionLabel.setRendered(true);
 this.regionMenu.setRendered(true);
 List<Region> regionList = regionFacade.getByPays(ps.getIdPays());
 for (Region rg : regionList) {
 this.regionItems.add(new SelectItem(rg, rg.getDesignation()));
 }
 }
 }
 }
 return null;

 }
Thanks