Government spokesperson Thitima Chaisaeng said that Yingluck will make a trip to Brunei on Saturday. She will go Indonesia on Monday, Cambodia on Thursday and Laos the following day.
All the PM's overseas trips would be just one day, she said, and she would not be staying overnight.
New Thai prime ministers traditionally pay their first visit to Laos, which shares many similarities with Thailand in terms of language and culture, and Yingluck has been criticised for choosing to go to Brunei first.
Brunei reportedly has a close relationship with Yingluck's brother, Thaksin, who has run away from a two-year jail term in Thailand on charges of corruption and abuse of power.
Thaksin stayed in the country for a while after fleeing Thailand after the 2006 military coup that ousted him. He now mostly lives in Dubai, but visits Brunei from time to time to meet his political supporters. He recently met ex-PM Banharn Silapa-archa, who is de facto leader of the coalition Chart Thai Pattana Party, there to discuss the portfolio quota in Yingluck's first Cabinet.
Officials earlier defended the criticism, saying Brunei is the first country that replied that it was ready to host such a visit.
They said Yingluck will spend only a few hours in Bandar Seri Begawan to have dinner with the Sultan of Brunei, Hassanal Bolkiah, and to introduce herself as the new PM. She will return home the same day.
It was her intention to make the visit as short as possible so that she could just introduce herself, and not to tackle any matters of import, the officials said.
In Cambodia, Yingluck is expected to fix damaged relations following the festering border conflict over Preah Vihear in recent years.