I'm in the process of doing this. First you need to get marriage certificate authenticated at DFAT, Sydney Passport office for me. $102 AUD per document. Then take to Thai Consulate in Sydney for legalisation. $25 AUD per document. All details available on Thai consulate website.
It is ok to ignore email. You can still do notification on line when due. Went through same process this month. You enter new entry date in notification.
Came back from Australia today. Couple in front of me had no accommodation booked. IO would not allow them entry. Sent them back from desk and told them no booking no entry.
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