Do I need a return ticket for entry into Thailand with a tourist visa?

We hope move to Thailand later this year for a 3-6 month stay. I know one needs a return flight ticket when flying into Thailand with only a passport, but it looks like you also need to have a return ticket when flying in with a visa. Is that true? We are getting a 2 month tourist visa with the hope of extending it once we are in Thailand. Any advice would be helpful.