Instructions here. Forewarned is forearmed!
If worse comes to worst, just say you’re Canadian. 
I read that last week. Many of the points are true, especially about wearing tennis shoes. Europeans just don’t do it.
Mind that I’m South American, but as far as Thailand is concerned that piece of advice is pretty much useless. 
Everyone wears crocs and tennis shoes, carry their cameras around their necks, women wear shorts, big brand names on clothes, eat at McDonalds or KFC, etc, etc…
One thing I noticed on the article, about holding the knife in the right and the fork in the left, I had no idea in the US it was customary to do it the other way around!
Baseball caps, overburdened backpacks, pasty white with red on top and a certain air of cluelessness are the dead giveaways. 
It isn’t. At least, it never was in my family. We were told, repeatedly, to always hold the knife in the right and the fork in the left.
Not the other way around, exactly. In the US, the traditional use is to cut food with the knife in the right hand, swiftly switch the fork and knife, and then pick up the food with the fork in the right hand. Softer foods are eaten with the fork in the right hand, sometimes using the edge of the fork to cut, and at such times the knife is left on the table or the plate.
Hmmm, I was always taught when I was a wee thing that one should never switch hands.
Diff’rent strokes, I s’pose.
Ignorant plebs
The fork should always be in the left hand and the knife in the right. At least that’s how they do it at the Nobel Dinner.
I agree that most of it is just 
errr we do that too.
Some stuff is really obvious (like maps and shorts, loudness, baseball caps as well) but on the whole it doesn’t really matter. If you live in a touristy location, you can spot tourists a mile away even when they actively try not to be conspicuous. It’s something in the eye - if you look puzzled, lost, quizzical or amazed by perfectly common stuff, yer a tourist all right. Hell, if you *notice *perfectly common stuff, it’s enough. Here in Paris, if you don’t look like a terminally depressed, grumpy, pissed off postal worker who’s about to whip out a shotgun and shell the crowd, doesn’t matter how you’re dressed, chances are you’re a tourist, too :).
I love playing that game, in the subway or in touristic spots like the Champs Elysées, around museums etc. - spot the tourist, then try and guess where he’s from.
One word:
plaid shorts.
One word:
not here, at least.
Also. I want to see somebody post the opposite guide to show them not-'muricans how to not look like not-'muricans in 'murica.
Another word:
White sneakers.
The linked article is quite correct about that - it’s really obvious. Also, clothing made of sweatshirt material (whatever that’s called), and whites that are nearly luminously white.
The fork/knife thing has advantages and disadvantages on both sides. Clearly trading hands all the time is dumb. But, when I was a kid it was hammered into me never to turn the fork (always tines-down in the left hand) so that it is a scoop - stabbling only. Which is equally dumb. And no elbows on the table, which is unbelievably arbitrary, IMO.
Oh, maybe my family learned these rules from your family. 
Funny, I just saw this on Reddit.
Not exactly the same, but similar.
Here’s one I learned: If you are tattooed and traveling to warm climate, or another country in summer, it would do you well to understand the implications of your ink there. Not all cultures approve of the practice, and in some places it can cause you trouble. In Japan for example, heavily tattooed men may find themselves labeled gangsters, and the locals reticent to help. In certain Middle eastern countries the process is forbidden, and displaying it will immediately get you labeled as a western tourist. Also remember that many cultures *might * view your art as appropriations of the native culture if you have traditional designs.
And they won’t let you into swimming pools or public baths, either.
My ex was a non-gangster inked Japanese fella. I don’t think any gangsters are getting his tattoos (Neptune symbol because he really likes Sailor Neptune, mermaid, dolphin) but it was still enough to get him banned from any of the onsen. Fricking annoying is what that was.
Do Europeans worry about trying to not look European when visiting the US?
Yes. They all buy white sneakers, shirts that proclaim “I love Virginia!” and wear baseball caps to fit in.
I did that. Walked around NYC wearing sneakers, a baseball cap and a varsity jacket 
(I was 18 at the time)
I live in a tourist town and I can spot them a mile away. They’re usually pasty white with some patches of sunburn, they wear stretchy or plaid shorts no matter how overweight they are, they’re the only ones filling up all of those surf and junk stores and they have a perennial queasy look from eating too many corn dogs at the boardwalk. They also block the sidewalks by walking 4 abreast and they’re looking everywhere except right in front of them. They think that the raggedy street kids are ‘hippies’ and take pictures of them like they’re another tourist attraction. They often have ‘Mystery Spot’ bumperstickers and they’re the only people on earth that would buy big plastic sunglasses where the frame is made to look like a woman’s legs. But, we love them because without them we’d have no economy other than the university and it wouldn’t be such a pretty town.
I’ve never understood the point of these lists. Who gives a shit if you look like a tourist? (You think we aren’t going to realize you’re an American because you don’t wear trainers? The games up as soon as we hear you speak.)
And the stuff about not wearing trainers (sneakers) is just bizarre. Most young British people wear trainers unless they’re at work.