Can I extend my visa after a border run to Satun from Phuket in Thailand?

IF you get a 30 day visa exempt entry as a US passport holder you can get a 30 day extension at the immigration office for 1900baht

BUT

IF a Russian passport holder gets a 30 day visa waiver entry they can ONLY get a 7 day extension denied stamp at the immigration office for 1900baht

Thanks you all to try to find out what the country of origin of the OP is and what the country of origin of the OP friends is. I had to read all the comments several times to understand what is going on. Would be so much more easy with a little information in the question.

What do you want to do by border run? Do you want to enter Thailand on exempt/waiver scheme or activate new entry on your multiple entry visa?

If former, 30days visa exempt entry can be extend for 30days at immigration office, 30days visa waiver on bilateral agreement entry cannot.

If later, entry on only multiple entry tourist visa can be done with 30days extension.

What nationality are you/passport?

Your profile says you are American.

You are allowed TWO LAND BORDER exempt entries each calendar year.

Having a visa does not count in the two allowed.

And upon a visa exempt entry you would get 30 days stay...

with added extension of 30 days available at local Thai immigration...1,900 Thai baht fee.

As you are living in Thailand since 2017, I suggest you get the correct visa to do so.

Thai Immigration is CHANGING and those with history of many entries using exempt entries, tourist and ed visas, with extensions like you are asking about now.

Good Luck to you... Be prepared if denied reentry. Its happening more and more at many border and airport entries.