Can I return to Thailand on a tourist visa after leaving for 3 months?

So you bought a tourist visa from a thai consulate in your country via the online eVisa system, came here, were stamped in for 60 days, took the one 30 day extension at the immigration office and now you've been out of the country for 3 months?

I would say buy another tourist visa online have proof of onward travel and you should be okay. They are looking at people who are trying to live here on free stamp (visa exempt) and/or tourist visa entries and if they will ask you anything at passport control it will be proof of onward travel