During July and August my wife and I took flights from Chek Lap Kok (Hong Kong), Don Muang (Bangkok) three times, Changi (Singapore) and Chiang Mai airports. Both of us were inadvertently carrying hand luggage that contained 13.5cm craft knives. The knives were in pencil cases with sketchbooks, in thin nylon bags. Mine was only noticed on the final leg of our journey out of Chiang Mai where the woman in charge asked if I was carrying a knife. I said yes, handed it to her and it was put in a desk drawer. My wife's knife was never noticed.
The more worrying event took place in Bangkok in the 1-7 departure gate area where we found an unattended bag in a corner close to the waiting-area seats. After watching it for 10 minutes to see if anyone claimed it, we mentioned it to an official at the departure gate. He thought it was rather amusing and called over other attendants to hear the story. He did say that if it was still there in 15 minutes he would take a look.
I suppose we must have been viewed as 'silly foreigners' because 40 minutes later, when we departed, the bag was still there and had not blown up.