Dimuth not out on132 and Dhananjaya de Silva (56) remain on the wicket.
The duo have now put up an unbroken 97-run partnership for the fourth wicket.
Pathum scored his second Test half-century off 56 balls before being bowled by Shannon Gabriel.
However, Oshada Fernando and Angelo Mathews were unable to score today.
They were both dismissed for 3 runs apiece.