Can I extend my 30-day tourist visa in Thailand for an additional 30 days?

Nope

Nope the only way you’ll get to stay any longer is by leaving the country and re-entering, if you don’t have an extensive history of doing this you’ll have no issues but some borders will expect you to spend at least a day on the other side of the border so some research into your preferred exit point will be needed if you want to avoid this.

Unfortunately no as James has said.

Sorry but you can ONLY get one 30 day extension of stay following your entry to Thailand as Visa Exempt.

You did not have a Thai tourist visa when you arrived into Thailand.

You could do a land border bounce... getting you a new 30 day Visa Exempt Entry.