Went to immigration this morning 10.00am and got told to come back tomorrow as too much people today, looks like this could become a pain in the arse every time I arrive.
Just been in the same situation, planned to fly with 2 days overstay, went to immigration for extension and they turned me away because the cost for 2 days fine (1000baht) is less than what it would have cost for the extension. I told the immigration police the story at the airport and asked if this is okay and if it would cause any problems in the future coming back in, they told me no problem.