It's hard to get use to at first as it seems every driver asks you 'Tuk Tuk Sir!' ...even when you just get out of one.
I've actually seen westerners flip the finger, be abusive and get agro when walking along. The best counter is to just smile and shake your head or wave your hand. Sure, you might have to do this a lot but most drivers will know you after a short time and just smile, I think a lot are just bored and want a chat.
Why ruin your day getting angry when after a while you actually learn to smile more and be more tolerant. I've seen people loose it and then see and hear the drivers laughing afterwards...maybe the joke is on us.
I once saw a marathon runner absolutely exhausted and coming near last when a Tuk driver resting in the back of his carriage yelled out laughing.. 'Tuk Tuk Sir!'... I nearly coughed up my coffee.
To live in Cambodia, love it.