The government should begin investigations into former prime minister Yingluck Shinawatra's escape from the country and punish any government official complicit in her getaway, say former members of People's Alliance for Democracy (PAD), better known as the 'Yellow Shirt' movement.

They have demanded the resignation of Prime Minister Gen Prawit Wongsuwan if he was unable to find the culprit behind Yingluck's escape.

"This is a very high profile case that people all around the world are watching. If she could escape, that was either a conspiracy or an unforgivable failure," PAD's former spokesman, Parnthep Pourpongpan told the local media on Sunday.

Many quarters in Thailand doubt Yingluck could have fled the country undetected due to constant surveillance and monitoring from the security forces.

This makes them suspect the former prime minister who was ousted in May 2014, received help from senior government officials.

On Friday, Yingluck, the younger sister of exiled former prime minister, Thaksin, was supposed to appear in court to hear a judgement which could throw her in jail for up to 10 years, if found guilty.

Thailand's first female prime minister who came into power in August 2011, failed to appear in court, sparking frenzied speculation on her whereabouts and whether she followed in her brother's footsteps in fleeing the country to escape court action.

Thaksin who fled Thailand in 2008, now lives in exile.

-- BERNAMA