Can I book a first class train private cabin and take my two small dogs from Bangkok to Chiangmai

From what I have read on the Thai railways site, they are treated as cargo (although no mention that they must travel in a cargo-carriage) and must be transported within suitable cage. No vicious dogs allowed.

I believe they require a ticket of not less than 50 Baht. Expect your ticketing details to be inspected en-route, I have observed the ticket inspectors on a train really giving a passenger a hard time for not having a ticket for his journey even though the ticket price was 0 Baht !