take another border or fly back to Thailand, Malaysia borders are little bit strange if you don’t go with agency. Had problems at Sungai Kolok and Takbai, but finally let me in
You will get overstay stamp and that looks always not good. Therefor it depends on immigration officer when you reenter Thailand. Some has no problems, other make problems. Therefor so many different answers from people.
The same person which did it for your friend can do it for you (owner/office of owner/agent), get in contact with them. It was no problem at my place. They also gave me screenshot for immigration office