I've wondered for a long time if there is a Buddhist [or Thai] equivelent to the Christian saying of 'I promise to god', 'i swear on a stack of bibles", 'my mother's grave', etc.

My wife says 'no translation', but I think she doesn't want me to know for obvious reasons......555

There is a satja, which is a solemn vow but is more to yourself then to the actual Buddha.

I have made two in my life.

ummm your wife is basically correct

The difference between a satja and its a promise is that you can only make a particular satja once.

You can not make it, break it, and make it again.

Many people believe that if you break a satja grave consequences will follow.

So, if you want a Thai Buddhist to swear that they will or won't do anything, how do you word it??

'do you "satja" this to be true??'

what has she done this time

The taking of satja vows, at least the one's I'm aware of, are quite a significant occasion.

They are conducted in front of a monk.

So, if you want a Thai Buddhist to swear that they will or won't do anything, how do you word it??

Say "Sabahn dai mai?" However, this is not specifically related to Buddhism.