this has happened to me 2 times the first I had a multiple entry tourist visa . The second I have non O marriage. IO did not stamp my passport at all but it was in the computer. My wife went to immigration at Chaengwattana and they stamped my passport.
I am never asked for onward ticket or 20,000฿ .I have a non O marriage. every time I fly back to Thailand .but I like to have the 20,000฿ or = in foreign currency on me just in case they ask.
In the future you can do a 90 report online even a reentry but for the reentry you must go to immigration but it’s very fast in and out . Also you can have someone do your 90 day report for you like a girlfriend, wife or friend.