Yamasaki, who will be based in Tokyo, spent 25 years working for Hitachi. Most recently he was general manager of IP business development and licensing. 
RPX, which was founded in 2008, provides a way for companies to defend themselves against attacks from patent trolls.
The company acquires dangerous patents and removes them from the market on behalf of its members, who pay a subscription fee.
It has 57 clients, including 12 based in Asia, and has acquired nearly 1,500 patents so far.
RPX says its clients pay between $40,000 and $5.2 million a year each in fees.