So, I have a tourist visa, single entry. I plan to extend it and get another month.

Now, the last date is Monday, 7th Dec' but it's a holiday - King's birthday (they changed the holiday date so it won't fall on Saturday). Immigration offices are closed.

In order not to "loose" days, is it possible to arrive at the 8th, pay the one day overstay and get another month?

Or, by doing so, will I invalidate my own visa, without the ability to extend it any further?

You loose nothing by doing the extension early. The extension starts at the end of your 60 day entry.

You can do it a couple of weeks early without a problem.

The Visa is extended from the visa expiry date ,not the day when you extend it .

Also, if the Immi office is closed for whatever reason on your day of expiry, they will not fine you or class it as an overstay , if you get the extension done on the next open day

"In order not to "loose" days, is it possible to arrive at the 8th, pay the one day overstay and get another month?"

• ​You can apply early. You don't loose days by applying early.
• The 30 day extension will apply from when your existing stay expires regardless how early you apply.
• If the immigration office is closed on the day your stay expires you can still get an extension on the first working day after without penalty.

"Or, by doing so, will I invalidate my own visa, without the ability to extend it any further?"

Your visa is only invalid after all entries are used or it has expired.

How certain are these extensions? Has anyone heard of someone's application for extension being rejected? I got an extension last time I was in Thailand in 2008 at the Jomtien office, but I remember feeling nervous about it. I forget the details, but I think I'd made some small error and the woman handling my application went ballistic and I thought for a moment she was going to refuse me.

Reason I ask is I that I'll be travelling to Thailand soon and want to stay 90 days and I'm not sure whether to get a 60-day single entry and then apply for an extension or get a double-entry and do a border run.

Edited October 21, 201510 yr by Verlis

The 30 day extensions are routinely done at immigration without a problem.

How certain are these extensions? Has anyone heard of someone's application for extension being rejected? I got an extension last time I was in Thailand in 2008 at the Jomtien office, but I remember feeling nervous about it. I forget the details, but I think I'd made some small error and the woman handling my application went ballistic and I thought for a moment she was going to refuse me.

Reason I ask is I that I'll be travelling to Thailand soon and want to stay 90 days and I'm not sure whether to get a 60-day single entry and then apply for an extension or get a double-entry and do a border run.

As long as you apply before the stay that you are extending expires you should never have a problem The application is simple although some offices do ask for proof of address if your living in a private residence.

What's the earliest I could apply for the extension? (I.E. how many days before my visa expires)

What's the earliest I could apply for the extension? (I.E. how many days before my visa expires)

You really need to stop worrying about it .

Its quite straight forward

Thank you all! Very encouraging.