You will only have one Amazon Associate account no matter how many websites/domains you have. Once Amazon approves your account for one domain it seems their scrutiny on additional sites under your account maybe less. Although this round about way to bypass what is already completely legal under Amazon's current rules should not be necessary.
There are forums out there legally making money off of Amazon Associates. You just need to be able to clearly show that you personally own and run the forum domain. This takes dealing with an Amazon employee who also clearly understands their own rules.