He started to practice under the coaches, Jayalath Senake Premawansa and Padmawathi, where he contested in 50 metres, 75 metres, 100 metres and 200 metres during school life. After seeing his talents, Anura Bandara, then Ambagamuwa Maha Vidyalaya coach, advised him to participate in the 400 metres. In 2000, he contested in Sydney Olympics. His best performance in a major global competition was in the
2001 World Championships where he reached the semi-final. In
2002 Commonwealth Games, he won the second place by recording a time of 46.80 seconds in the 3rd preliminary round. Then in the 4th heat of the semi-finals, he recorded a time of 46.48 seconds and qualified for the semi-finals. But in the 2nd semi-final, he finished in 6th place with a time of 45.79 seconds and did not qualify for the final. At the
2002 Asian Athletics Championships, Thilakaratne won the bronze medal by finishing in 45.73 seconds. ==Post-retirement==