I have rented a few places in a few different parts of Thailand (Including Chiang mai before) I have always had to sign for a years contract but after the initial year it has been on open with a 30 day notice.

I recently moved into a new house and they want me to sign a contract every year. Now I fully agree with the first year as they need commitment, but I liked the fact that once that year is up you are free to then look around if you want to with no obligation either way. Whats the chances of finding something that you want at the exact time of your contract expiry?

Whats other peoples experience of this? it it usual? are there any legal rules about this subject?

Would be interested to know.

Lastly, it isn't a "Farang" thing as I was away and it is all in a Thai' s name.

Depends on the owner. You can agree to whatever you want, be it another yearly contract or X months notice.

Personally, I'd rather sign a contract every year, just so I know the owner won't suddenly decide to raise the rent or sell the unit and tell you to move. But, it up to you to negotiate if you'd like to go month-to-month after the first year. It would be a good idea to talk with the owner in advance of signing that first year contract just so everyone is clear about your expectations.