Let's start from the bottom up.
It depends on where you are. Some people swear by Sperry Top-Siders, and I tend to wear them a lot when I'm stateside. While I like Sperrys, I find that they make you pop out as an American when you are overseas. If you're Santa Barbara or on Long Island, being an American isn't that big a deal. When you're walking on the beach in Phuket, you might not want to be as easily pegged. As a result, I like to go with the summer loafer/driving shoe. I have a
pair of these in blue and in saddle leather brown, and they don't break the bank. If you want to go a little more upscale, try
Tods. Tods makes fantastic shoes, although they cost a little more. Not as big on the online thing, but they have a store in Miami, one in Huntington Beach and another in Beverly Hills, one in Vegas, as well as in many coastal population hubs round the world. If you're living in a halfway decent country, there will be a Tods somewhere. I own a pair of the
driving shoes, they're fantastic. Loafers are a little more upscale, a little more European, and look a little more sophisticated than your sperrys. I'd splurge if I had the cash.
Some people can pull of shorts, others cannot. Let's just assume you're wearing pants, because everyone can pull off pants. I have a few pairs of pants that I rock on a regular basis, all of them pretty lightweight. You need a pair of white pants for the tropics. If you spill when you're eating often, these pants will make you learn quick. It doesn't really matter where you get your pants from, but I love Bonobos. Idk about international shipping, but if you're in America, give these a shot.
These are the white pants I own.. You'll also probably want a pair of khakis, a pair of navy pants, and maybe another pastel color.
For shirts, button down oxfords all the way. Make sure they fit well, but not too tight. You can unbutton a few buttons and roll up the sleeves if it gets hot. Shirts, like pants, it doesn't really matter where you get your shit from, as long as it fits. You'll want a few white ones, as well as some other light colors.
By going with the loafer+pants+oxford look, you'll generally look good and sophisticated, which can be great during the day, regardless of location. If you want to dress it down a little, you can throw on some nice leather flip flops if you're in a real beach town instead of loafers, or you can rock shorts. For shorts, go with 9" inseam if you're taller than 5'10 or 7" if you're shorter. 11" is too long for most guys. If you're built like a rugby player, rock those 5" inseams all day, but if you're skin and bone short shorts look a little ridiculous.
At the end of the day, this has to be calibrated a little bit for your location and what you're doing. This should be totally fine for most places in SEA, the Caribbean LA, Miami, and Southern Europe. If you're in the favelas in Rio rolling around in R$1,000 loafers is probably not a good call, same thing if you're in the townships outside of Cape Town or Durban.
It all boils down to where you are. You'll dress very differently if you're in Saint-Tropez then if you are in Gulf Shores, AL. Often times, you want to look good, but not stand out. Standing out can mean trouble if you're in a third world location, where crime can be an issue and police forces range from ineffective to non-existent.