BANGKOK (Reuters) -Thailand's annual headline inflation unexpectedly rose in June but at its slowest pace in 22 months, and the commerce ministry on Wednesday lowered its forecast for consumer prices rises for the whole year.

The headline consumer price index (CPI) increased 0.23% in June from a year earlier, compared with a forecast fall of 0.1% in a Reuters poll, and against May's 0.53% year-on-year rise.

The slower headline pace was due to lower food and energy prices and a high base last year, which should continue to help hold down consumer prices, the ministry said.

It was the second straight month that the headline CPI dropped below the central bank's target range of 1% to 3%.

In June, the core CPI was up 1.32% from a year earlier, compared with a forecast for a 1.4% rise in the poll.

"Compared with other countries, Thailand has very low inflation," ministry official Wichanun Niwatjinda told a briefing.

The ministry predicts the headline CPI will rise 0.77% year-on-year in the third quarter and 0.62% in the final quarter of the year, he said.

"That means full-year inflation will be at 1% to 2%," he said, adding that was cut from the 1.7% to 2.7% projected previously.

In the January-June period, annual headline inflation was 2.49% and the core rate was at 1.87%.

In May, Thailand's central bank raised its policy interest rate by a quarter point to 2%. It will next review policy on Aug. 2, when some economists expect no rate change while others see a further hike.

(Reporting by Orathai Sriring, Kitiphong Thaichareon and Satawasin Staporncharnchai; Editing by Martin Petty and Jamie Freed)