Earlier this year I traveled to bangkok and got the 60 day visa.
I later learned that you don't need a visa if you are leaving before 30 days.
Is the process any different when you are at the Bangkok airport? When I had the 60 day visa I gave them the visa document+passport. Next time I go for 15 days do I just need to tell them I am leaving before 30 days? Do I need to provide proof of the flight I am leaving on?