I will need to extend my tourist visa 30 days which expires in a couple weeks. Can I go to the local immigration office and extend it early? If I make an extension before the date of expiry, will the 30 days be tacked onto the date I apply for the extension or will it be tacked onto the date my tourist visa expires?

Tourist visa expires May 5 + 30 days = June 3. If I go in tomorrow, April 25, will the extension then expire April 25 + 30 days = May 23 or will it be stamped June 3?

I'm American if that makes a difference. Thanks for your help, I'm new to all these rules

It will be added to your current stay so nothing lost is doing early.

Go tomorrow, the 30 days will be tacked on to the end of your current permission to stay not 30 days from the date that you apply!

Wow, thanks for the quick reply! Good to know.

I went yesterday to do my extension. Had stamp "admitted until 24 APR", got extension stamp "up to 23 MAY" Small mistake but can happen, so check what you get.