As the National Council for Peace and Order (NCPO) permitted Ms Yingluck's overseas trip beginning July 20 to August 10, a source close to Ms Yingluck said that she would leave Thailand on July 23 and return on August 10.
She will visit several European countries with her son Supasek Amornchat who will have school holidays then.
They will visit Germany, Switzerland and France where they will attend a birthday party of her elder brother and former prime minister Thaksin Shinawatra.
Mr Thaksin reportedly plans to hold a small party with his family members and people close to him.
A very small number of key figures from the Pheu Thai Party will be present as the NCPO is controlling politicians' movements to preclude an international display of political enthusiasm for Mr Thaksin.
Sek Wannamethee, director general of the Department of Information and spokesman of the Ministry of Foreign Affairs, said Ms Yingluck followed normal procedures in requesting NCPO approval for her overseas trip. He said he did not think she planned to seek political asylum.
Mr Sek also said that the foreign ministry was following overseas anti-NCPO movements led by former Pheu Thai Party leader Charupong Ruangsuwan.
He commented that the movements happened in the countries that were friendly to Thailand so their governments would not support them.
Mr Sek added that the Thai embassy in Phnom Penh was verifying a report that Ekapop Luara, a Thai lese majeste suspect, was shot dead in Cambodia.