Thailand's Information, Communication and Technology (ICT) ministry said it was investigating the hijacking of the PouYingluck tweet feed for around 20 minutes early on Sunday.
Yingluck, the sister of ousted former leader Thaksin Shinawatra, was lambasted on a variety of subjects in eight posts, including her response to recent serious flooding and a number of key government policies.
"How can she protect the country, if she cannot protect her own Twitter account? Think about it," said the final post.
Yingluck, who was propelled to victory in a July 3 election with Thaksin's backing, has put forward a raft of measures, including a rise in the minimum wage, aimed at his poor and rural support base.
One of the hacked posts questioned a high-profile promise to give tablet computers to schoolchildren, saying it was no substitute for education reform, while another accused Yingluck and her government of cronyism.
The tweets said that rather than "image building", the premier should look to find long-term solutions for two months of flooding that has left more than 200 people dead and inundated huge swathes of the country.
Thailand deployed about 10,000 soldiers on Friday after Yingluck ordered the army to take action to assist flood victims.
The username PouYingluck refers to the Thai leader's nickname, Pou, which means crab.
ICT spokesman Songkran Taechanarong said the ministry was hunting for the hacker and was considering closing the prime minister's twitter account.
Thaksin, who remains a highly controversial figure in politically-divided Thailand, was removed from office by royalist generals in 2006 and lives abroad to avoid a jail term for corruption.