Worrying too much. I've transported desktop PCs multiple times between UK and Thailand and UK and China. Just put into the cardboard box the tower case originally came in and check it in as normal. Never been stopped or questioned.
Once too 25 PC motherboards to China in a cardboard box, along with loads of cables, PSUs etc in a big box.
Over the years flown into BKK (mostly with Ermirates) with tools, power drill etc, trolley jack, couple of bikes, couple of HiFi systems, part of a car exhaust system etc etc. Been asked a couple of times 'what's in the box?'. Answered honestly and no further checks. Amazingly never had anything damaged in transit either. Only had trouble in India (they confiscated two Melton Mowbray pork pies) and Nigeria (confiscated a souvenir mug they said was a potential weapon!).