public static function ThemeDetail(){
        $objectManager = MagentoFrameworkAppObjectManager::getInstance()
                ->get('MagentoFrameworkAppResourceConnection');
             $connection= $objectManager->getConnection();
             $theme_table = $objectManager->getTableName('theme');
             $theme_data = $connection->fetchAll("SELECT * FROM ".$theme_table);
             if(!empty($theme_data)){
                foreach($theme_data as $theme_name => $value){
                 $themeArray[] = array('name'=> $theme_data[$theme_name]['theme_title'], 'version'=>'2.0.5');
                }

              return $themeArray;
             } else {
              return FALSE;
             }

      }

MagentoFrameworkAppConfigScopeConfigInterface
MagentoStoreModelStoreManagerInterface
MagentoFrameworkViewDesignThemeThemeProviderInterface

public function getThemeData()
    {
        $themeId = $this->_scopeConfig->getValue(
            MagentoFrameworkViewDesignInterface::XML_PATH_THEME_ID,
            MagentoStoreModelScopeInterface::SCOPE_STORE,
            $this->_storeManager->getStore()->getId()
        );

        /** @var $theme MagentoFrameworkViewDesignThemeInterface */
        $theme = $this->_themeProvider->getThemeById($themeId);

        return $theme->getData();
    }

Use directly objectmanager is not right way, use __construct() way to define your class inside block is better way to use coding standard.

public static function ThemeDetail(){
        $connection = $objectManager = MagentoFrameworkAppObjectManager::getInstance()
                ->get('MagentoFrameworkAppResourceConnection')->getConnection('MagentoFrameworkAppResourceConnection::DEFAULT_CONNECTION');

    $version = $objectManager->get('MagentoFrameworkAppProductMetadataInterface');


             $theme_table = $connection->getTableName('theme');
             $theme_data = $connection->fetchAll("SELECT * FROM ".$theme_table);

             $themeArray = array();
             if(!empty($theme_data)){
                foreach($theme_data as $value){ echo $value['theme_title'];
                 $themeArray[] = array('name'=> $value['theme_title'], 'version'=>$version->getVersion());
                }
             } else {
                return FALSE;
             }

           echo "<pre>";print_r($themeArray);exit;

      }