I just came back in from Malaysia via Wang Prachan this morning after my tourist visa expires. Got a 30 day visa exemption no problems. Had to stay one night in Malaysia.
yes looks like you better go to immigration and hope they admit their error and show you some leniency, then do a border run asap. Good luck, it's so easy to get caught like this under the current confusing and ever changing system.
yes I accidentally overstayed recently. I paid the 500 baht per day fine and then paid to extend my visa. The overstay counts as part of the extension so you will have 30 days left minus how many days you have already overstayed. They did not stamp my passport as having overstayed.
I was planning to just cross the border and return overland not travel to Penang. Either Satun or Ranong. As I'm in Krabi and that seems to be the closest borders I can ride to.