Is it true that I can get a 60-day visa exemption on arrival in Thailand, and how do I extend it for an additional 30 days?

Will arrive in Bangkok on 31st January for onward travel to Koh Samui for 3 months visiting friends instead of my usual 60 days, in the past I have only had my passport stamped with a 30 day visa and have extended it on the island for another 30 days.

I keep hearing that this is now 60 days with the option to extend for another 30 days, is this true and if so is it done automatically on arrival or do I have to ask for it. And do I need to show any documents e.g. my return flights.

Thank You.