The Colombo Stock index ended 0.12 percent firmer at 6,448.21.
Shares in Dialog Axiata Plc rose 2.3 percent, while Cargills (Ceylon) Plc gained 2.7 percent and biggest listed lender Commercial Bank of Ceylon Plc ended 0.7 percent up.
Turnover was 1.33 billion rupees ($8.65 million), with foreign buying accounting for around 85.8 percent of the turnover. Last year's daily average was 915.3 million rupees.
Foreign investors bought a net 876.8 million rupees worth of shares on Thursday, extending the year-to-date net foreign inflow to 3.99 billion rupees worth equities.
They bought equities worth 18.5 billion rupees last year, and 633.5 million rupees in 2016.
"Market is up on foreign buying in Commercial Bank," said Hussain Gani, Deputy CEO at Softlogic Stockbrokers.
"Foreign investors are driving the market. Local investors are waiting for the situation to improve to take the next move."
President Maithripala Sirisena said over the weekend that he would handle the economy, taking over from the government's main coalition partner, led by Prime Minister Ranil Wickremesinghe.
The comments have sparked uncertainty over the future of the coalition government, analysts said.