When packing for Bangkok you might want to consider what the locals are wearing. In some countries, even hot ones, you might be expected to modestly wear pants. In case you hadn’t heard, it’s hot in Bangkok. But fortunately when it comes to clothing, Bangkok is about as casual as it gets. Shorts and skirts are the norm. Flip flops and t-shirts are standard.
Many Thai are averse to getting dark skin (thus the tons of skin-whitening products on the market) so you will also see people in long sleeves despite the heat. Outdoor workers may actually be covered head to toe with broad-brimmed hats, gloves and a handkerchief over their faces! Not recommended! But take that as a warning about the sun and pack your sunscreen and a hat for any extended time in the sun such as at temple ruins in Ayutthaya or in the shadeless Wat Arun compound at mid-day for example. There is no law that says all light-skinned Westerners have to look like lobsters and it’s just going to make your time here a bit more comfortable.
There are a couple of exceptions to the casual rule. One is the upscale restaurant or club. If you are splurging for a martini with a stunner of a view at Sirocco, men will need nice pants, collared shirts and closed shoes; women have more leeway but flip flops are out. This goes for nightclubs such as Q Bar as well. The other dress code is for temples. Shoulders must be covered and though shorts/skirts are often acceptable, they should be to the knee. Places where long pants are expected will typically rent or loan a pair of baggy slip-over pants to visitors. For more on temple etiquette, check out this NileGuide Chiang Mai blog post which contains some advice on the subject.
Around town, however, it can be a bit of a free for all. Flip flops are the footwear of choice (though I recommend sandals for better foot support in consideration to Bangkok’s often dodgy sidewalk surfaces and to put a bit more between you and some pretty disgusting pavement.) T-shirts are fine as are exposed shoulders for the women. Think light-colored, breathable fabrics for the heat. The light colors are also nice at night to attract fewer mosquitoes.
Sunglasses are a good idea, and if you forget to pack them, the streets are filled with places to buy them cheap – most likely knockoffs though. Make sure yours block the UVs.
And one more rather important matter: a little note on risky colors…