I can't help with cycling there much (although one of these days I'll get a bike while I'm there - my wife and I have a home in Thailand, but it's in Bangkok and I don't much fancy cycling in the city).
All I can say is that I've traveled round that part of the country a fair bit (I'm a sucker for Khmer ruins) by car, bus, train, motorbike, and I reckon it's generally pretty laid-back and I think I'd be happy enough to cycle there. I'd probably use backpacker guesthouses and be sure to take my bike into my room.
I did notice a few stretches of cycle path in the areas last year, including one short one along (I think) the main Saraburi-Nakhon Ratchasima road, but they're very scarce and intermittent.