The holiday rules are for the 30 days excemption. You get the stamp overstay (with mention not fined due to holidays), but don't have to pay the 500 bahts/day fee.
You can buy also the re-entry stamp at intenational rairport when leaving Thailand in case you want not longer stay at immigration after receiving your year extension ๐.
For airline tickets I know that some airlines request a ticket number. I booked last time a single ticket with AirAsia Phuket to Singapore for 30โฌ to be on the safe side and avoid stress at check-in ๐
Some arlines want to see your exit-ticket of Thailand (can be a bus or trainticket) before day 31. Please check with your airline to avoid any troubles.