frm_add_form_style_class

This example checks the WPML language and uses styling settings for an RTL style instead of the regular style for your form.

add_filter( 'frm_add_form_style_class', 'add_style_class', 1 );
function add_style_class( $class ) {
  $lang = apply_filters( 'wpml_current_language', null );
  if ( $lang == 'ar' ) { // change ar to your language code
    remove_filter( 'frm_add_form_style_class', 'FrmStylesController::get_form_style_class', 10, 2 );
    $class .= 'frm_my_style_class frm_rtl'; // replace frm_my_style_class with your rtl style class
  }
  return $class;
}