BANGKOK (Reuters) - Thailand's headline inflation rate in September slowed from the previous month and less than expected, data showed on Wednesday, but above-target consumer prices reinforced expectations of further interest rate hikes.The headline consumer price index (CPI) rose 6.41% in September from a year earlier, slowing from August's 7.86% increase, helped by easing prices of energy products, according to commerce ministry data.That compared with a forecast rise of 6.60% in a Reuters poll.The core CPI index was up 3.12% in September from a year ago, also less than a forecast rise of 3.20%.Inflation is expected to fall further in the fourth quarter of this year, the ministry said in a statement.Last week, the Bank of Thailand raised its key interest rate by a quarter point to 1.00% to contain inflation that has hit multi-year highs. It will next review the rate on Nov. 30, when most economists expect a further, gradual hike.