It's simple.
First set "display stock" to Yes
admin panel>system>setting>options set display stock to "YES"
now
//catalog>controller>product>product.php
Find (around line 282)
if ($product_info['quantity'] <= 0) {
$this->data['stock'] = $product_info['stock_status'];
} elseif ($this->config->get('config_stock_display')) {
$this->data['stock'] = $product_info['quantity'];
} else {
$this->data['stock'] = $this->language->get('text_instock');
}
Replace With
if ($product_info['quantity'] <= 0) {
$this->data['stock'] = $product_info['stock_status'];
} elseif ($this->config->get('config_stock_display') && $product_info['quantity'] <= 5) {
$this->data['stock'] = $product_info['quantity'];
} else {
$this->data['stock'] = $this->language->get('text_instock');
}
Hope this helps