Can I extend my 30-day visa by just walking into the immigration bureau in Thailand?

Do it Monday. Get there before it opens. It’s like DMV. Bring your resident form TM 30 from hotel or apartment. Also bring a passport photo and your passport. In the back of the line is a table with the form fill it out and get in line. At the front of the line hand your paperwork to the girl. She will use a glue stick to put your photo on the paperwork you just filled out. She will give you a plastic number. Go to the next area that has seats. Wait until your number is called and go in another office with about 10 seats, they will call you to a window. Hand them the passport and paperwork that was already assembled by the girl in the first line. Pay them 1900 baht in cash. Go outside and sit again, make jokes with the guy from Kuwait about car-pit bom-bing his country. He will laugh. Soon they announce to go to the table and a girl will handout about 5 passports. If you’re late expect them to close entirely for lunch. Don’t be late. Your passport will add 31 days to your previous exit date. Good luck.

I suggest that you demand to be allowed to stay for as long as you want, trust me it'll be ok

Yes.30 days

Go fill up form pay money

The extensions are routinely done all day long at immigration offices, and are probably the most common thing they deal with hundreds of times a day in tourist towns. From your questions in comments, you seem overly concerned when there's no need to be.

Make sure you have your TM30 form before you extend

Yes just walk in and ask.

@Jermaine *****

This is the TM.7 extension form. You can download if you want.

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There's no such thing as a 30 day visa. I assume you're talking about visa exempt which isn't a visa at all, it's just an entry stamp.

If you enter with visa exempt you should be able to apply one time for a 30 day extension at your local immigration office. There are many holidays coming up though when immigration will be closed.