Thai/Cambodian guys who cross the border with you and do the talk somehow to officers. 3 weeks ago I was there and got approached by this guy, at that time my visa still valid for another 3 weeks so didn’t bother to do it. I spoke to the guy this morning and he told me it will take 30 mn, you have to pay 1800 baht for Cambodian stamp and pay the guy some money. Hope that help.
I tried to apply for it couple weeks ago, their requirement was the company must have 150 million USD turnover and have branch in thailland. Most company don’t disclose their revenue unless there are listed in stock market!!