On successful paid orders for all payment gateways others than Bank wire, cheque or Cash on delivery, you can use dedicated woocommerce_payment_complete hook located in WC_Order payment_complete() method instead of more generic hook woocommerce_thankyou, like:
add_action( 'woocommerce_payment_complete', 'action_payment_complete', 10, 2 );
function action_payment_complete( $order_id, $order ) {
// Here add your code
}
Note that you can use defined $order_id and $order function arguments. Also this hook is only triggered once, avoiding repetitions.
For Bank wire (bacs), Cheque (cheque) or Cash on delivery (cod) payment methods, As the shop manager confirm manually that order is paid by changing order status, you can use the dedicated hook woocommerce_order_status_changed as follows.
add_action( 'woocommerce_order_status_changed', 'bacs_cheque_cod_payment_complete', 10, 4 );
function bacs_cheque_cod_payment_complete( $order_id, $old_status, $new_status, $order ) {
// 1. For Bank wire and cheque payments
if( in_array( $order->get_payment_method(), array('bacs', 'cheque')
&& in_array( $new_status, array('processing', 'completed')
&& ! $order->get_date_paid('edit') ) {
// Do something
}
// 2. For Cash on delivery payments
if( 'cod' === $order->get_payment_method() && 'completed' === $new_status ) {
// Do something
}
}
Note that you can use defined $order_id and $order function arguments. Also this hook will be triggered once, on order status change, avoiding repetitions.
Related: After a successful payment, What hook is triggered in Woocommerce