Thai security forces destroyed a suspect motorbike Thursday at a major Asian security forum, causing the sound of a large blast, but found no evidence of a bomb, the army said.

A sniffer dog alerted police to the bike about 300 metres from a hotel complex in the resort island of Phuket where US Secretary of State Hillary Clinton was attending the conference, they said.

Security forces destroyed the motorcycle using a high-pressure water gun designed to take out the electronics of any possible explosive device, Thai army Lieutenant General Kanit Sapitak told reporters.

"No explosives were found at all. We think it may have been traces of urea, or it could have been traces of fireworks," Kanit said.

He apologised for causing any alarm, but said the incident "reflects the highest level of security which we have enforced, which we think that we have been able to enforce effectively as you can see".

Security has been tight for the Association of Southeast Asian Nations (ASEAN) Regional Forum following anti-government protests in April which derailed a major summit of Asian leaders in the seaside resort of Pattaya.