I think it's the same glue that holds any relationship together. It's all about give and take, genuine equality, and bear in mind, even the thickest person in the world can sense when you consider yourself to be a cut above them. Despite all the horror stories you read, not all Thai women are after money and/or a lavish lifestyle. Hell, to use one of Sarge's old expressions, I can barely afford a bucket to pee in, and yet my wife is still with me after 11 years. And, to brush aside another myth, the "sick buffalo" story is just that, an invented fairytale. Sure the odd girl has used it, but nobody I know who's married to a Thai has come across it.
I would quite honestly say my marriage is the same as most marriages are after 11 years.....sometimes we laugh together, other times we argue, she has her space, I have my space, and neither of us try to change one another. We are who we are, and we're happy with that. Sure we don't kiss and cuddle as often as we did 10 years ago, but that's to be expected, or at least that's how I see it.
Okay, I do have one huge advantage in my favor.........my wife doesn't enjoy watching TV at all, and neither do I, so no soaps to bother me, and no football to bother her.
In a nutshell.....it's been the happiest and most enjoyable period of my life.

Don't try to impress me with your manner of dress cos a monkey himself is a monkey no less - cold fact