Tens of thousands of supporters of Thaksin Shinawatra, the former Thai prime minister, have gathered for a rally in the capital Bangkok as political tensions mount across the country. A small explosive was detonated outside the sports stadium as people arrived to hear Thaksin address the crowd by telephone. There were no reports of any casualties in the explosion, which occurred despite about 1,500 police officers being deployed to maintain security. Another 2,500 army troops are on standby to assist if necessary, with police estimating that around 40,000 people have turned out to hear Thaksin speak. Thaksin, who was ousted from power in a 2006 military coup and recently convicted in absentia of breaching a conflict of interest law, is expected to address the crowd on Saturday evening. Selina Downes, reporting from Bangkok for Al Jazeera, said the arena was full to capacity, with others waiting outside the stadium for Thaksin to deliver his address. The former leader's speech comes just two days before Thailand's parliament votes on a new prime minister.