So, a bit of an oops on my part. Tickets are purchased. I'll be leaving the Kingdom the 89th day. 

 

I have a 60 day tourist visa stamp. I'm setting the reminder to go get the 30 day extension. The 60th day will land on Sunday. So, the closest I can go to immigration will be friday. If they set the start date as that day. My extension will end two days before I leave.

 

Options?  

They will give you 30 extra days so you should be fine.

Set your reminder to go get your 30-day extension a week before your 60-days ends.  Your extension-time begins at the end of your existing permission-of-stay, so you don't loose any days doing it this way.  No reason to wait until the last minute.  Your total of 90-days will include your first and last day in Thailand.

Day 1 of the 30 day extension will be day 61 regardless of how early you apply.

 

You should apply before the current 60 days ends, but as it falls on a Sunday you can apply on the next working day.

13 hours ago, slowlyman said:

So, the closest I can go to immigration will be friday.

You don't need to wait until the last minute. The extension is added onto you 60 day permission to stay regardless of when you apply for/receive the extension.

With the recent changes to the overstay rules, does anyone actually know (not guess) how they react to a 1 or 2 day overstay?  The rules were set up I think to deal more with the longer term overstays. In the past it was just 500 a day, and apart from the paperwork no real fuss. About 8 months ago I ended up going to overstay by about 2 days but went and got the 1900 baht extension in case they got shirty.

9 minutes ago, Gas666 said:

With the recent changes to the overstay rules, does anyone actually know (not guess) how they react to a 1 or 2 day overstay?  The rules were set up I think to deal more with the longer term overstays. In the past it was just 500 a day, and apart from the paperwork no real fuss. About 8 months ago I ended up going to overstay by about 2 days but went and got the 1900 baht extension in case they got shirty.

At the current time, a short overstay does not have immediate repercussions, unless one immediately returns visa exempt. I would still avoid it. I could imagine a time in the future when even short historical overstays might enter into immigration official decision making.