KUALA LUMPUR, July 18 (Reuters) - Malaysia has maintained its August export tax for crude palm oil at 8.0% and raised its reference price, a circular on the Malaysian Palm Oil Board website showed on Thursday.

The world's second-largest palm exporter calculated a reference price of 3,880.86 ringgit ($831.91) per metric ton for August. July's reference price was 3,839.63 ringgit a ton.

The export tax structure starts at 3% for crude palm oil in a 2,250 to 2,400 ringgit-per-ton range. The maximum tax rate is set at 8% when prices exceed 3,450 ringgit a ton. ($1 = 4.6650 ringgit) (Reporting by Danial Azhar; Editing by John Mair)