Tucked away in a refurbished factory building in southwest Singapore, Shopback’s headquarters houses only 50 people, just a quarter of its workforce. The affiliate marketing firm may only have a fraction of the employees that giants like Facebook and Google have, but Shopback has big dreams – to offer businesses a more efficient way of reaching their customers. In Southeast Asia, Shopback has gained traction thanks to its cashback app, with more than 8 million users and 2,000 merchants. When…