• I want to know the hidden spots not in a travel guide book!
• I want to look for a host who are willing to provide us a space for 3 people

which is the cheapest way to go to Chiang Mai from Bangkok? Is there any cheap airlines?

Yes, Air Asia if you book in advance
www.airasia.com
www.flyorientthai.com
You can fly for 1800-2000 Baht take only 1 hour 20 minutes.

Bus would take 10 hours cost around 600 Baht or sleeping train would take around 14-15 hours and cost from 590 Baht for fan to 980 Baht for A/C