No, that was not specifically asked for however they do ask for your flight itinerary which has my departure date on it. If you want you can see exactly what they ask by going through the visa process on the
your question is unclear. My departure date is about 50 days away and I am only traveling from USA/BKK/USA. I only provided the documents as I related. Your question states ..."within 60 days of your arrival?" with the key word being "WITHIN". I can only answer your question correctly in the future once 60 days transpire from my arrival in Bangkok. However, since further documentation will not required I can relate my belief that no, I won't be providing proof on onward travel when I arrive.
I provided my airline itinerary which detailed my arrival/departure dates, booking of hotel in BKK (2 days) and provided the house address of my wife where I will stay for at least a month before heading back south to Koh Lanta.