Today I called in to a couple of places in Dan Sai, both within walking distance of the event. Both fully booked on Friday 1st, although one one had a large room available,suitable for 6 people for 2500Baht for the 2nd July only. The first one had more than doubled their room prices to 2500 Baht for a double room and they were all booked. These are the only 2 days in the year they can get these sort of returns on their rooms, so you cannot really blame them.
Finally booked a room at a resort, but its a nice one, with well located individual cabins about 500M or so along the Nakhon Thai road after the big Wat on the LHS. Nice location, but not really walking distance, seems good condition and includes breakfast. Standard price 800Baht. Pi Ta Kon weekend, 1,200 Baht, so not so much inflated. They still have 3 or 4 rooms available, but you will probably have to pay part of the cost for them to accept a booking. Phone number 0862337103. Its a Thai name that approximates to Drijutarat Resort.