We stayed at Pha-Thai House for a week and loved it. The family who runs it are warm, approachable and professional, and made everything easy, particularly the concierge - I didn't catch her name but we were really impressed with her conscientiousness.
Our room was very comfy, functional and tastefully decorated. Beds are excellent and the place is nice and quiet at night, with great aircon. Breakfast isn't included in the room rate but is available from 7-11am, reasonably priced, and a la carte - we enjoyed the fruit salad and the banana pancakes. The gardens around the house are beautiful and there are lots of friendly resident animals - dogs, cats, koi, tortoises (!) - but staff were careful to make sure they didn't bother anyone.
If I'm ever back in Chiang Mai, this place would be my first choice. Thank you for looking after us!