HKD10.318 如何轉寫英文長寫

Actually, the english version that you written above was wrong.
That should be ten dollars and thirty one cents only.
it would be corrected to 2 decimal place for HKD 10.318. In other words, you should write 10 dollars and thirty two cents only.
I guess you are writting a cheque, but it doesn't make sense to write more than 2 decimal place for a cheque. Beside, if your cheque book is provided by hong kong's banking, you do not have to specified "hong kong dollar" when written in english.
hopes it's helps!!

The european way of using the decimal point in numbers is different from the way it is used in Asia. Nowadays it is the ISO standard to use decimal for the separation of every three number. For example: HKD100.000 means Hongkong dollars one hundred thousand not one hundred dollars.
HKD102.450 means Hongkong dollars one hundred and two thousand four hundred and fifty. Therefore, HKD10.318 means Hongkong dollars ten thousand three hundred and eighteen.

It is not correct to write HKD10.318 = Ten Hongkong dollars and thirty-one cents.....