@Benjamin ********
because until not long ago even on the official site they used the wrong wording ? Because even a few days ago the Bangkok Post used the wrong wording ?
The problem is not tourists not understanding English, but the officials and the Bangkok Post spreading the wrong information because of their poor command of English or whatever.
The Bangkok Post quoted the chief of immigration division :
"..must fill in (..) at least 3 days ahead of their expected arrival in Thailand"