I am wondering if I can get away with a one-way ticket to Hong Kong on a tourist visa. The reason I am not keen on getting roung-trip is I don't intend on returning to Thailand. I will go back home to the US after my trip to HK. Does anyone have experience with this?

What are you saying

1) you are in Thailand and have a tourist visa to HK but no onward ticket from there or

2) you are not yet in Thailand, have a tourist visa for Thailand and a O/W ticket to HK

In which country do you hope to 'get away with it'?

What nationality are you? I landed in Hong Kong in April from UK, then Macau and then China and at no point did I have to show proof of departure I just filled out a landing card and got a 6 month stamp - although I assume you may be a US citizen if thats where you are returning too! Not sure then but I didn't really see anyone being asked for proof of departure - everyone was through in two mins!

It's unclear exactly what you're asking but...

You don't need a visa to go to HK (If you're American).

If you are flying from Thailand to HK a one-way ticket should be no problem.

I worked in HK a couple of years ago and made a number of trips in/out and never had to show return tickets. Same when I took the wife there a couple of times.