What comes from Thailand in small parcels labeled "cosmetic"?

If small brown mailing envelopes were arriving fairly often in the mail, with postage and customs stickers from Thailand, handwritten return addresses, and the word “cosmetic” listed under “contents,” what would you think they contained?

The parcels are about the right size to hold, say, two decks of cards or a small bottle of aspirin in a box.

I’m assuming it’s something ordered online, and I have my doubts that it’s actually cosmetics.