I come back from Laos with some T-shirts that I think are cool and then I become the butt of a joke

It's probably indiscernible to you, and it's a small difference to me, but it's very obvious to Thais. The difference between "บ" and "ข" is a small bend where the small loop is but that's the difference between a "B" sound and a "K" sound in the Thai alphabet. However, notice that this shirt is from Laos. Thai and Laos languages use similar alphabets but there many of these small changes in letters that prevents Thais from easily reading Laos and Laotians from easily reading Thai.

As the joke of my t-shirt goes, the Laotian letters read "Beer Laos." That's fine and dandy, good for me I have a beer t-shirt. But the Laos letter "B" looks like the Thai "K". That is, they switch the two letters above. So, in Thai, the t-shirt does not translate to "Beer Laos", instead it translates to "Laotian son-in-law." This was not a small joke back in my town. Everyone thought it was hilarious. Everywhere I went people would read the shirt, laugh and then start the rhetorical questioning. As their joke goes, I went to Laos for just one week and but found a wife, married her, and come back to Buakhao with the t-shirt to prove it. Sure, it might not be as funny to you, but to Thais it just doesn't get much better than word-play jokes like these. And if there's one thing better than a joke, it's a joke about a falang.