diff --git a/inc/class-wooviet-onepay-domestic.php b/inc/class-wooviet-onepay-domestic.php
new file mode 100644
index 0000000..8a6666b
--- /dev/null
+++ b/inc/class-wooviet-onepay-domestic.php
@@ -0,0 +1,86 @@
+<?php
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+/**
+ * The class to handle the domestic OnePay gateway https://mtf.onepay.vn/developer/?page=modul_noidia
+ *
+ *
+ * @author   htdat
+ * @since    1.3
+ *
+ */
+
+
+
+
+class WooViet_OnePay_Domestic extends WC_Payment_Gateway {
+	/**
+	 * Constructor for the gateway.
+	 */
+	public function __construct() {
+		$this->id                 = 'wooviet_onepay_domestic';
+		$this->has_fields         = false;
+		$this->order_button_text  = __( 'Proceed to OnePay', 'woo-viet' );
+		$this->method_title       = __( 'OnePay Domestic Gateway (by Woo Viet)', 'woo-viet' );
+		// @todo - check the method description
+		$this->method_description =  __( 'OnePay supports all major bank ATMs in Vietnam.', 'woo-viet' );
+		$this->supports           = array(
+			'products',
+		);
+		// Load the settings.
+		$this->init_form_fields();
+		$this->init_settings();
+		// Define user set variables.
+		$this->title          = $this->get_option( 'title' );
+		$this->description    = $this->get_option( 'description' );
+		$this->merchant_id          = $this->get_option( 'merchant_id' );
+		$this->access_code          = $this->get_option( 'access_code' );
+		$this->secure_secret          = $this->get_option( 'secure_secret' );
+
+		// @todo: the sandbox option
+
+		add_action( 'woocommerce_update_options_payment_gateways_' . $this->id, array( $this, 'process_admin_options' ) );
+	}
+	/**
+	 * Initialise Gateway Settings Form Fields.
+	 */
+	public function init_form_fields() {
+		$this->form_fields = include( 'onepay/domestic-settings.php' );
+	}
+	/**
+	 * Process the payment.
+	 */
+	public function process_payment( $order_id ) {
+		$order          = wc_get_order( $order_id );
+		return array(
+			'result'   => 'success',
+			'redirect' => $this->get_pay_url( $order )
+		);
+	}
+	/**
+	 * Get the OnePay pay URL for an order.
+	 * @param  WC_Order $order
+	 * @return string
+	 */
+	public function get_pay_url ( $order ) {
+		$access_key = $this->access_key;
+		$secret = $this->secret;               // require your secret key from 1pay
+		$return_url = $this->get_1pay_return_url();
+		$command = 'request_transaction';
+		$amount = $order->get_total();   // >10000
+		$order_id = $order->id;
+		$order_info = sprintf( 'The payment for the order number %1$s on the site: %2$s', $order->id, get_home_url());
+
+		// @todo: review and see the file do.php in the demo files
+
+	}
+
+	// @todo review this function
+	/*
+	public function static get_return_url(){
+		return WC()->api_request_url( __CLASS__ );
+	}
+	*/
+}
diff --git a/inc/onepay/domestic-settings.php b/inc/onepay/domestic-settings.php
new file mode 100644
index 0000000..baa53d4
--- /dev/null
+++ b/inc/onepay/domestic-settings.php
@@ -0,0 +1,71 @@
+<?php
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+// @todo - ver 1.3 - check all texts
+/**
+ * Settings for 1Pay Gateway.
+ */
+return array(
+	'enabled' => array(
+		'title'   => __( 'Enable/Disable', 'woo-viet' ),
+		'type'    => 'checkbox',
+		'label'   => __( 'OnePay Domestic Gateway (by Woo Viet)', 'woo-viet' ),
+		'default' => 'yes'
+	),
+	'title' => array(
+		'title'       => __( 'Title', 'woo-viet' ),
+		'type'        => 'text',
+		'description' => __( 'This controls the title which the user sees during checkout.', 'woo-viet' ),
+		'default'     => __( 'OnePay Domestic Gateway', 'woo-viet' ),
+		'desc_tip'    => true,
+	),
+	'description' => array(
+		'title'       => __( 'Description', 'woo-viet' ),
+		'type'        => 'text',
+		'desc_tip'    => true,
+		'description' => __( 'This controls the description which the user sees during checkout.', 'woo-viet' ),
+		'default'     => __( 'With OnePay Bank, you can make payment by using any local Vietnam ATM card.', 'woo-viet' )
+	),
+	'api_details' => array(
+		'title'       => __( 'API Credentials', 'woo-viet' ),
+		'type'        => 'title',
+		'description' => sprintf( __( 'Enter your OnePay API credentials. Contact OnePay to have your credentials %shere%s.', 'woo-viet' ), '<a href="http://onepay.com.vn/home/en/contact-us.html">', '</a>' ),
+	),
+	'merchant_id' => array(
+		'title'       => __( 'Merchant ID', 'woo-viet' ),
+		'type'        => 'text',
+		'description' => __( 'Get your Merchant ID from OnePay.', 'woo-viet' ),
+		'default'     => '',
+		'desc_tip'    => true,
+		'placeholder' => __( 'Required. Provided by OnePay.', 'woo-viet' )
+	),
+	'access code' => array(
+		'title'       => __( 'Access Code', 'woocommerce' ),
+		'type'        => 'text',
+		'description' => __( 'Get your Access Code from from OnePay.', 'woo-viet' ),
+		'default'     => '',
+		'desc_tip'    => true,
+		'placeholder' => __( 'Required. Provided by OnePay.', 'woo-viet' )
+	),
+	'secure_secret' => array(
+		'title'       => __( 'Secure Secret', 'woocommerce' ),
+		'type'        => 'text',
+		'description' => __( 'Get your Secure Secret from from OnePay.', 'woo-viet' ),
+		'default'     => '',
+		'desc_tip'    => true,
+		'placeholder' => __( 'Required. Provided by OnePay.', 'woo-viet' )
+	),
+	/*
+	// @todo: Add more help info later
+
+	'help_title' => array(
+		'title'       => __( 'More info about 1Pay', 'woo-viet' ),
+		'type'        => 'title',
+		'description' => __( 'You can see more info at this link.', 'woo-viet' )
+	),
+	*/
+
+);
\ No newline at end of file
diff --git a/woo-viet.php b/woo-viet.php
index e056150..2b4b469 100644
--- a/woo-viet.php
+++ b/woo-viet.php
@@ -119,11 +119,24 @@ class WooViet {
 		load_plugin_textdomain( 'woo-viet', false, basename( dirname( __FILE__ ) ) . '/languages/' );
 	}
 
+
+	public function add_gateway_class( $methods ) {
+		$methods[] = 'WooViet_OnePay_Domestic';
+		return $methods;
+
+	}
+
 	/**
 	 * The main method to load the components
 	 */
 	public function main() {
 
+		// @todo: ver 1.3 check this
+		add_filter( 'woocommerce_payment_gateways', array( $this, 'add_gateway_class' ) );
+
+		include( 'inc/class-wooviet-onepay-domestic.php');
+
+
 		if ( is_admin() ) {
 			// Add the admin setting page
 			include( WOO_VIET_DIR . 'inc/class-wooviet-admin-page.php' );