The rules that use the vocabulary item "thousand" are:

<up_to_four_digits>

<digit> thousand

<scale_number-gapsout_null-gapsin_null>

a thousand

one thousand

one thousand five hundred

two thousand

two thousand five hundred

three thousand

three thousand five hundred

four thousand

four thousand five hundred

five thousand

five thousand five hundred

six thousand

six thousand five hundred

seven thousand

seven thousand five hundred

eight thousand

eight thousand five hundred

nine thousand

nine thousand five hundred

ten thousand

fifteen thousand

twenty thousand

twenty five thousand

thirty thousand

thirty five thousand

forty thousand

forty five thousand

fifty thousand

fifty five thousand

sixty thousand

sixty five thousand

seventy thousand

seventy five thousand

eighty thousand

eighty five thousand

ninety thousand

ninety five thousand

one hundred thousand

a hundred thousand

one hundred fifty thousand

two hundred thousand

two hundred and fifty thousand

two hundred fifty thousand

three hundred thousand

three hundred fifty thousand

four hundred thousand

four hundred fifty thousand

five hundred thousand

five hundred fifty thousand

six hundred thousand

six hundred fifty thousand

seven hundred thousand

seven hundred fifty thousand

eight hundred thousand

eight hundred fifty thousand

nine hundred thousand

nine hundred fifty thousand