They are sprayed, but not w/ formaldehyde! My coconut creds: Since the 90s& 2000s I've been to Thailand abt 2 dozen times, India abt 11 times, Hawaii abt a dozen too. I've sucked down coconuts w/ daily gusto since discovering them in Venezuela in the late 70s when I spent a summer there, rediscovering them in Jamaica in the 80s, living with a local guy, again for a whole summer.
Coconuts, commercially grown for export, are a mono-crop & are sprayed mostly w/ pesticides to prevent mite infestations, which can wipe out or severely cripple whole fields & affect vast areas. Commercially, they are of course fertilized as well. When I'm overseas, I buy my cocos from local families who subsidize their family income by selling them to their local community, ie they are pretty much organic or totally organic.
Now, this formaldehyde rumor that circulated strongly online a number of yrs ago is BS, though Thai coconuts, like all fresh imported, non-organic produce, is definitely sprayed before entering the USA. It's a sad fact, but its hardly unique to Thai coconuts only. Thai coconuts imported into the USA are thus not the very best way to consume coconut as they are sprayed while being grown & afterwards too, but they aren't 'super bad' either in comparison to other commercial foods.
And it is one of the more enjoyable tasty treats for me, & that counts pretty high in my book of priorities. I REALLY miss being in the tropics, on many many levels, that's for sure. Where cocos are cheap, fresh & plentiful, as is the fresh fish. In Sri Lanka, South India & even Panama, I most savor King Coconuts, those small, super sweet yellow coconuts, so named for a very good reason. Last time I was in Panama, I brought back a litre of homemade King Coconut oil, wish I had mailed a frickin case of 24 bottles back & put them in cold storage. If I ever retire, in my dreams, it'll be to the tropics, to a King Coconut/Chocolate farm