Have you tried using a thai proxy? One of those free online ones you can easilly find on google. I tried going there but it gives me the same 403 error, personally I think it's some server issues they're having, but I can't test the proxy atm since my wireless is kinda failing. =S
I also had no trouble accessing it, you know, once I figured out which button was the register button, then which of two buttons got me to the point that allowed you to enter your information and create your log in and such.
Edit: Does this link work for you: http://lime.goldenso...isterStep2.aspx
That gets to the point where you actually enter info.