Vietnam's domestic coffee prices fell to four-month lows this week, tracking international prices, while trading was thin in Indonesia at the end of its main harvest season, traders said on Thursday.

Farmers in the Central Highlands, Vietnam's largest coffee-growing area, sold coffee at 30,000 dong ($1.29) per kg on Thursday, according to traders.

January robusta coffee settled down $24, or 1.9%, at $1,240 per tonne on Wednesday.

"There have been virtually no transactions in the past weeks as buyers are waiting for fresh beans from the upcoming season," a trader based in the region said, adding that new beans wouldn't arrive until mid-November.

"Farmers make no profit at this price considering the production cost is already at 33,000 dong per kg."

Traders forecast the output to be around 30 million 60-kg bags for the 2019/20 crop year starting October 1.