I've been bidding for a nice pair of classic trainees on ebay. A colleague reckons if they're shipped here Thai customs will hold them until I pay duty on them. Is that right?

Shouldn't do - I've ordered two pairs of shoes online in the last two months and were both delivered without problem. Not from ebay though.

If you are the successful bidder, ask the seller to state in the customs declaration that it's a gift rather than state actual value of the shoes.