Agree, can work out more cost effective then renting, plus as said above no reclaiming deposits back hassle.
Had a 3 month contract in Malaysia couple of years ago, and got an AirBnB for the duration. Got supper discount, Elec/Water/WiFi all included, plus gym and swimming pools and panoramic views of Singapore. Paid 1 month at time of booking, them monthly in advanced, as per AirBnB regs. Showed rental contract to Immigration at Airport, and stamped in for 3 months no probs.
However, with Thailands Immigration and the fact they want to know where your staying, then might be an issue if questioned, especially if staying beyond 90 day (assumes you're not border hopping).
Did look at 3 month stay in the past, as great long stay discounts, but once I questioned the potential Landlord on TM30 they all stopped communicating!