1. Veet Hair Removing Mousse (I left mine at home because I was worried about aerosol cans in checked baggage)
I looked and looked in Bangkok - supermarkets, Watsons, other pharmacies - NO! and they had no idea what I meant. Next time I'm taking it!

2. Travel-sized kettle for those early-morning or late night cups of tea or coffee - room service not a satisfactory solution.
We have one of these and usually take it + coffee mugs + teabags/coffee. Last trip we left it at home.

Got to hotel after midnight and had to wait ages for the in-room hotpot thing to boil.