Thinking about the best way to Optimise my upcoming stays in Thailand.

I Have my return leg of a flight booked to go back to Bangkok from Dublin at the end of September. I was on a STV visa from Jan to July, those are being discontinued now and are single entry so weighing up my options.

I plan to go to Australia for a few weeks over the Xmas/NY period.

Can I stay in Thailand for 90 days on a single entry tourist visa which would get me through to the December period that I will be going to Australia?

Would a METV be the best option when returning back to Thailand from Australia? Not sure I would have time for visa processing since it’s over the Xmas period and I will only be staying for two or three weeks.

I’m an Australian and Irish citizen