Thailand's Government Pension Fund (GPF) plans to lift its overseas investment ceiling to 40 percent from 25 percent as it looks to boost returns, the fund's Secretary-General said.

GPF is the country's largest pension fund, which manages civil servants' savings. The ceiling has been proposed to the Ministry of Finance for its approval, Sombat Narawutthichai told reporters.

"We expect to get a gradual approval of 5 percent per time," he said, adding that the fund was seeking higher returns from overseas investments, including bonds and equities.

The fund now invests 60 percent of total assets in domestic bonds, 4 percent in overseas bonds, 12 percent in Thai equities, 15 percent in overseas equities, 5 percent in property and the rest in other asset types, he said.