suspense in thrillers is built through many different ways.
the music is a main contribute. it can suddenly change from a normal soundtrack to a more alarming frightening soundtrack that indicates to the audience that something is going to happen.
another way suspense is built is through cliff hangers. cliff hangers make the audience go on the edge of their seats, movies often use cliffhangers at the opening of the movie to make the audience want to continue watching. they can also use them at the end of a film if they are planning on making a sequel of it. this gives the audience the idea that the film will be full of suspense.