Most scratched off bottles are that way because they are "grey-market" goods. If it's cut off/scratched off -- then its 99% most likely grey market. It is common for online retailers. They are scratched off so that you can not trace back to the source of the product of where it had come from (so the over-quota reason may be valid too) before going to a discounter -- or any other place it wasn't meant to in the first place (e.g. most "discount" Creeds are from the Middle East-Asia region with their serial numbers scratched off before getting loaded with thousand other bottles in a cargo container) They are real and authentic, but do so in order to hide some shady business practice of some kind from the buyer. Nevertheless, this way, everyone makes a profit -- the manufacturers in Europe, the department stores, the discounters, and even the buyer gets it for less!
Also -- with the serial code -- you can check with some nice manufacturers for the actual age of the bottle. My other hypothesis is that it may be scratched off because it is way beyond shelf life.
They are supposedly illegal in the EU, but "okay" in the US -- and Thailand probably doesn't care at all.