Just found this reported alleged court rukling from Hua Hin - another tourist spot with hotels unhappy about air bnb.
https://www.bangkokpost.com/news/general/1467442/airbnb-bookings-illegal-court-declares
A cut and paste from Findthatproperty.com...
Can I Legally Rent my Property via Airbnb in Thailand?
Although Airbnb is hugely popular, it receives constant criticism and opposition from the hotel industry. Members of the hotel industry view Airbnb as a form of short-term letting and a direct form of competition – many people say that Airbnb is actually illegal in Thailand and that it should be prohibited.
Two major laws provide some clarity on this matter – the Hotel Act and the Condominium Act. The hotel act of 2004 states that it is illegal for anyone owning 3 or more units within a single building to operate a short-term let. In most cases, therefore, Airbnb is perfectly legal as most people rent out their own home or a single property. Ensure you are familiar with any taxes that you may be liable for when renting out your Thailand property.
The condominium act, however, states that short-term lets are only allowed with the explicit permission of the condo owner. If the condo prohibits short-term leases then we advise against breaking the rules as you could face severe backlash.
If you live in Thailand and own your condo it could be worthwhile renting your property through Airbnb – the potential to earn additional income is great and providing you meet the specified criteria, it is perfectly legal to create a short-term letting venture!