My tourist visa expires on Monday 09 February and unfortunately I wont be able to get to Bangkok immigration until Tuesday 10 February in order to apply for an extension (one day overstay).

Can anybody see any problems that might arise at immigration on the one day overstay or would I just be obliged to pay the extension fee of B1900 and the 1 day overstay of B500.

I would have been able to travel to immigration on 09 February but I see its a public holiday.

Any comments would be appreciated.

You can get an extension at any immigration office.

They will charge you 500 baht overstay and the 1900 baht for the extension.

They will be a little more understanding since the 9th is a holiday but they will still charge you the overstay.

You don't have to wait until the last day to do your extension. The extension is from the date your permit to stay ends not from the date you apply.