How can I determine minimum order to give discount

You can use the wc_payment_discounts_apply_discount filter for it.

Here one example that you can use creating a new plugin or in your theme functions.php:

function custom_wc_payment_discounts_min_order( $avaliable, $cart ) {
	$subtotal     = $cart->cart_contents_total;
	$min_subtotal = 100;

	if ( $min_subtotal <= $subtotal ) {
		return true;
	}

	return false;
}

add_filter( 'wc_payment_discounts_apply_discount', 'custom_wc_payment_discounts_min_order', 10, 2 );

Great !
Many thanks!

Hi,

I updated WooCommerce to version 2.4.6 but this code not work now.

Could you help me please?

Many thanks.