Ah, the point of posting this is discussion and this is a good one.

I personally see a good contract as a good starting point in terms of defining the relationship boundaries. I'm guess I'm old school. I care about three things being defined in my contract, my pay, any extra duties, and my hours. Everything else is open to negotiation and in a good relationship, neither person will push beyond certain boundaries.
Example, a contract may not make provisions for taking part in an English camp, but heck if I am a teacher at the school and they are holding an English camp then I will go ahead and take part. If it's a once in a semester or less occurrence then I'm ok with it. If the school has parent teacher night, then I will be there. I don't need it to be in my contract. I saw all of this based on a good relationship with the school.
If a school starts demanding I come in and stand at the gate every morning or if they demand I take part in just too many activities or they just piss me off then no I am not going to take part in the english camp or the Parent-teacher night. Why? because the relationship is bad. Once the relationship is damaged, you only have the paper to hold it together.
What's next? I've seen it enough times. Once the relationship goes south, you need to start looking for a new job because it won't get any better and the school, once you have to hold it to the contract, they will do anything and everything to screw you over.
And that's what Steve was getting at.
Once you start falling back on the paper, the deal is already in trouble.
If you have to remind your school admin to follow the contract then you know it's just a matter of time before they will try to screw you over. If you want to save the job, then look at repairing the relationship.
I'll give an example. I had a boss who dicked me over on some overtime work I did. A teacher had left midterm and I covered their classes. The first month I was paid the correct rate, but in the second month, the rate magically changed. Why? She didn't need me to do the overtime anymore. It was a few thousand baht and had me considering quitting. I also realized there was NOTHING I could do to get the lost overtime.
My wife had just taken a new job so I wasn't anxious to pull up roots so I examined my options. I was working with a crooked boss(who hasn't?) but more than that, there was a damaged relationship. I could walk but have a bad reference. I did something different. I bought the admin some chocolates and visited with her. I told her how sorry I was for reacting the way I did to the overtime and other bs. I improved the relationship enough to finish out the year and I left with a good reference.