Just because you are backpacking, doesn't mean you have to slum it. If you can gather a big enough group of people, either friends that come with you on your journey or other trustworthy backpackers. Then there are short term rental houses available in most parts of Thailand. I have linked an example of one that actually was down the road from where I stayed in Phuket. I was staying in a hotel with 7 others. If we had pooled our money, we could have stayed here for US$350, which would have worked out US$10 cheaper per night each.
A beautiful 4 bedroom villa, that sleeps eight, with your own pool!