What is the process for entering Thailand with a 60-day tourist visa obtained online?

Show print of visa at immigration on arrival. They will stamp you for 60 days. You may need to show airline on check in too

First of all, print out the email, that is your visa. Make sure you present it with your passport at the entry point, and then check your stamp in your passport after you step away to make sure everything is okay since it's much easier to fix right then and there.

Then keep the printed visa with you in the event you decide to get an extension or do anything else at immigration, they will want to see it again.