Go to onwardticket.com you can purchase a flight to Laos for 12.00 usd. I have done this many times just in case but I have never been asked when I only have a one way ticket to Thailand. Better safe than sorry. I now have a multiple entry retirement visa, soon to be switched to a marriage visa.
You can also have an agent get you a bank account for about 5000 baht on a tourist exempt.