I had the same thing happen to me. I saved the 60 day visa for a future trip. And did a weekend trip to Cambodia and re-entered Thailand 30 day Visa Exempt.
If in Pattaya, go to Bangkok Bank on 2d Road, near Soi 6. I was able to open an account there 2 years ago, on Visa Exempt stamp. Just needed to get a Certificate of Residence at Jomtien Immigration, based on TM 30 filed by hotel. Piece of cake. And they are always very helpful everytime I do business there.
They probably have arrangements for you to take a different van or bus on the Cambodian side of the border. You should call to get clarification from them