Normally you just show your passport and get stamped in. At the airports they want your boarding card as well.
For all tourist entries you formally are required to show an onward ticket within the days you’ll get stamped in for, at least som nights accommodation or an invitation to stay privately and cash equal to 20K baht. This is rarely checked in the immigration unless they’re looking for a reason to deny you because of excessive travel history. With your still quite clean history my best guess is that you’ll be fine only showing your passport.
Personally I think you should be fine with your plan. You’ve stayed in Thailand for a total of 110 days this year and you’ve also spent some days on a tourist visa last year. Objectively speaking you’re still a tourist and not someone trying to live or misusing tourist solutions for long term stay in Thailand.
No need to apply for a visa if you’re entitled to visa exemption. If you have a recent previous excessive travelling history in and out of Thailand a tourist visa could slightly raise your odds to get allowed entry, but your safest bet is a border bounce with a professional transport company.
I guess you mean the one year extension of stay. Anyway this is correct, no rule has changed and I’ve never heard of any immigrations with deviant practice either.