Bugs grow big in Thailand, besides their frightening size, most of them can pack a painful bite or sting, and some are even deadly. Read this before you start messing with Thailand’s most dangerous insects and bugs.
Mosquitoes.

Mosquitoes (see photo above) may not look fearsome or threatening, mosquitoes don’t have a painful bite, but they can transmit potentially life-threatening mosquito borne diseases.
Dengue fever alone kills thousands of people every year in Thailand, it is also a fact that diseases spread by mosquitoes have killed more people than all the world wars and natural disasters. I think that qualifies the mosquito as potentially one the most dangerous things in Thailand.
The Giant Centipede.

This monster centipede (see photo above) is commonly known as the “Vietnamese Centipede”, “Chinese Red Headed Centipede” and “Asian Forest Centipede”. The giant centipede can grow up to 15 inches long in Thailand, it is a fearsome predator and it will bite if provoked. The giant centipede delivers an incredibly painful and venomous bite which can result in a nasty infection, you should seek medical help. I rate the giant centipede as the scariest bug in Thailand.
Asian Giant Hornet.

Hornets are well renowned for their aggression when provoked, hornets grow to huge proportions in Thailand, making these one bug you don’t want to mess with.
You will commonly experience a giant hornet flying around you. Most people’s first reaction is to run like hell, if you try to swat it or spray it you may only make it angry, and we all know about angry hornets.
It’s best just to sit it out until it passes. Hornet stings can be extremely painful, I have heard the pain of a hornet sting described as “searingly hot” and “comparable to an electric shock”, a sting on a hand will often swell up like a football. This makes the ‘Giant Hornet’ Thailand’s biggest, badass flying bug.
Big Scary Spiders.

There is no shortage of big, hairy, scary spiders in Thailand, including tarantulas, black widows, giant orb spiders, and huntsmen.
Spiders have a very famous fear factor, which means the big hairy spiders found in Thailand put the fear of god in most people. Spiders are usually not aggressive but they can give you a nasty, mildly painful bite that could become infected if not properly cleaned.
Spiders are widespread in Thailand, species such as the Huntsman Spider commonly make their way indoors, residing in kitchen cupboards, and sinks, or scurrying across the floor, often resulting in a fearful scream. Big hairy spiders are the most commonly feared bugs in Thailand.
Scorpions.

Scorpions are found mainly in forests and rural areas of Thailand but don’t be surprised to find them in the cities, especially if there is any scrubland or parkland close by.
There is many a traveler’s tale on the Internet describing encounters with scorpions in Thailand. The encounters usually result in someone getting stung by a scorpion when putting on their shoes or getting dressed.
The moral of the story is “don’t leave your clothes on the floor”, and always shake your shoes before you put them on. Scorpion stings are said to be about as painful as a bee sting, the smaller the scorpion, the more venomous it is.
Like most bug bites and stings, there is a danger of allergic reaction, often serious, but it’s thought that scorpions found in Thailand are relatively harmless. I’d have to say scorpions are Thailand’s “biggest bug with a sting in the tail”.
Caterpillars.

Although they are often very beautiful and colorful, there are some species of caterpillar in Thailand that should be considered dangerous, one such example is the Stinging Nettle Caterpillar. The spines of the caterpillar are similar to fiberglass, they stick to the skin and are extremely irritating. The real danger is that they get in your eyes, in this case, you should seek medical help.
Paper Wasps.

At first glance, you might mistake them for a hornet, but paper wasps bear more resemblance to a large flying ant. The Paper Wasp has an elongated body, often marked with black and yellow bands, but it has various different colors. Quite often they appear to be bumbling around like they are lost. They are quite docile but they can give a mildly painful sting.
More Nasty Bugs in Thailand.
Some of the larger ant species found in Thailand can give you a nasty nip, be especially wary of red ants if you’re a golfer. If you happen to tread on a nest of red ants they will soon be swarming up your leg and biting the hell out of you in seconds.
At some point during your stay in Thailand, you have a Praying Mantis inadvertently land on you. Don’t be alarmed, they are quite harmless, you may be able to coax it onto its back legs and box your finger, it might bite you if it becomes annoyed, but it only delivers a slightly painful nip.