Do I need a return flight to enter Thailand on a Non O Retirement visa with plans to extend?

Hi all.

If entering Thailand on a Non O Retirement 90 day visa, are you expected to have a return flight booked to be able to enter the country, even though your intention is to apply for a 1 one year extension prior to the expiry of your 90 day visa?

Also, how do you apply for a multiple exit/entry permit once your 1 year extension has been granted?

Thank you.