I've flown with Ryan Air, BA, American Airlines, Air France and Malaysian and never had my hand luggage weighed or seen it done or heard of it done or seen equipment round about boarding to do it. Airline is probably more relevant than destination. They care more about size, if it's the right size then so long as you haven't filled it with something weird then you aren't likely to be significantly enough over.
5kg is a lower than normal amount though. I just booked a flight with Jet Star (Asia's answer to Ryan Air) and it's 10kg. IIRC Ryan Air is 10kg. Are you sure that's right?