Every country in Southeast Asia has their own local produce, but I personally think Thailand reigns supreme in regards to variety and tastiness (I'm only a smidge biased as a Thai person). As a country with no seasons other than "hot," we are able to grow lots of fruits that other places simply can't. While you may not be able to find everything year-round you're sure to never leave Thailand empty-handed — or should I say empty-stomached. Stop by any of Thailand's many markets and you should be able to get your hands on these exotic fruits.
Jackfruit (kanoon)
Weighing up to 100 pounds, the intimidating jackfruit is not only incredibly versatile, it's also extremely tasty! If you eat the fruit when its ripe you'll notice that it is sweet with floral notes and a chewy consistency. If you get your hands on a canned unripe jackfruit you can also use it as a meat substitute that's perfect for BBQ pulled pork.
Lychee (linjee)
One of my favorite fruits (and undeniably the best artificial candy flavor) lychee can be grown in tons of different places, including the States! After cracking open the red shell of a lychee (the color is how you can tell if they're ripe) you'll find a pale, pitted fruit with the texture of a grape but far more sweet and tart. Other than eating them fresh I also love using lychees for martinis.
Mangosteen (mong-kut)
Sweet and slightly creamy, mangosteens are referred to in Thailand as "The Queen of Fruits." You'll need a knife to cut through the fruit's hard purple shell but the soft flesh hiding inside is well-worth the effort. When eating a mangosteen you'll notice some segments have seeds while others do not, if you come across one with a seed just spit it out!
Durian (toorian)
While the shell of this fruit might look similar to a jackfruit, trust me, they're totally different. The meat inside of a durian is not only creamier than that of a jackfruit, but it's a lot more potent. As someone whose grown up around durian the smell doesn't bother me (in fact, I kinda like it) but I know some foreigners who can't stand it. You'll notice certain places like airports, cabs and hotels will even have signs forbidding you from bringing the fruit on the grounds, but don't let that scare you, it's called "The King of Fruits" for a good reason.
#SpoonTip: When purchasing durian you don't want to buy one that is overly ripe and yellow. Go for one that is lighter in color with a firmer texture.
Rambutan (ngaw)
Having grown up eating this fruit I never found their hairy appearance strange, but looking at them now I could definitely understand why some people shy away from them. Related to the lychee and longan, the rambutan has a slighter thicker shell (use a knife!) and a coarser, more almond-shaped seed. Rambutan has a milder flavor than a lychee and you'll also notice that it's a little harder to strip the flesh from the seed.
Longan (lumyai)
Sometimes called the "Dragon Eye Fruit," longan's are in the same family as lychees and rambutans. Once you've split open the smooth brown shell, you'll find something that looks similar to a lychee in shape but with more translucent flesh, giving it that "eye" resemblance.
Dragonfruit/Pitaya (gaeow mung-gon)
You might be able to find this fruit frozen and blended at your favorite smoothie-bowl spot, but trust me, they taste better when they're fresh. The most common variety of dragonfruit will have a pink exterior with green leafy "skin" and white flesh with tiny black seeds. During certain seasons you may also be able to find other dragonfruits including the ones with yellow skin or pink flesh. In terms of flavor and texture the fruit is most similar to a kiwi, albeit with no sour notes.
#SpoonTip: Squeeze some lime juice on pieces of dragonfruit if you find the flavor too mild.
Guava (faraang)
Another favorite of mine, guava is perfect for people who love chowing down on apples or crispy pears. Always in season, Thai guavas are a common snack with locals and can be found quite easily. With a mild flavor and satisfying crunch you might find this being the fruit you eat the most on your trip to Thailand.
Pomelo (som-o)
Similar to a grapefruit, this giant citrus is another one of my favorites (when I can find it). With light yellow or pink flesh, the flesh of a pomelo has a firmer texture than other citric fruits, making it popular in traditional Thai dishes. The flavor of a pomelo is milder than that of a grapefruit or orange, having none of the sweetness or sourness of either fruit.
Rose Apple (shom-poo)
In a shape reminiscent of a pear, the rose apple has a light and crispy texture that is both juicy and airy. Flavor-wise the fruit is watery with a hint of sweetness and you can find them in both red and green varieties.
Custard Apple (noi na)
Aptly-named, the custard apple is perfect for anyone looking to indulge in sweets without the added calories. Sweet with a soft interior the custard apple is best eaten with a spoon and a hungry tummy.
Langsat (longong)
After taking off the rubbery skin of the langsat you'll find translucent segments of fruit, eat each segment individually and spit out the seed you find inside. The flavor of the langsat is quite sweet but with a hint of tartness.
Snake Fruit (salak)
Named after its scaly, reptilian-looking skin, the snake fruit happens to be one of my least favorite exotic fruits. Besides looking pretty weird I also find the fruit too acidic and sweet for my tastes — but who knows, you might like it!
Sapodilla (la moot)
I've only had this fruit once and I won't lie, I wasn't a huge fan. With a pretty uninteresting exterior (at least compared to some of the other exotic fruits on this list), a sapodilla is sought after for its super duper sweet interior (which was way too sweet for me). To eat the fruit you slice it in half and eat it with a spoon, taking care to avoid the seeds.
Coconut (ma prow)
A crucial part of Thailand's culinary culture, the versatile coconut is used in everything from curries to ice cream. You may be able to pick up coconut water at your local Whole Foods, but fresh Thai coconuts are way more tasty. They're cheaper, too — you can buy a whole fresh coconut for a buck here. Try getting that deal in the States!
Passion Fruit (sawa-rod)
The passion fruit itself might resemble a weird alien egg, but trust me, it's totally harmless. With dozens of tiny little seeds covered in a sour orange pulp you're not going to want to try this fruit on its own. You're better off serving it in drinks or topped on other fruits in need of a sour kick. Also, you should avoid biting into the black seeds, they're flavorless and way too crunchy.
Rambai (ma fai)
I know people who've lived in Thailand their entire lives who still haven't tried this, so consider yourself very lucky if you can get your hands on this obscure little fruit. If I were to describe a rambai I would say it's a combination of a mangosteen and a langsat — the shell is thin like a langsat but has segments like a mangosteen. With a creamy texture you'll find that this fruit is sweet but with a sour kick.
Now that you've had a brief introduction into some of the more exotic fruits you can eat in Thailand you've just gotta find them. Good luck!
Here are more articles on Thailand:
The Beginner's Guide to Authentic Thai Food
8 Markets Every Foodie Should Visit While in Bangkok