Former prime minister Yingluck Shinawatra is expected to receive approval from Gen Prayuth Chan-ocha, chief of the National Council for Peace and Order (NCPO), to travel to Europe on Sunday night.
Ms Yingluck has sent a letter seeking formal permission to leave the country to Gen Prayuth, who led the May 22 coup that ousted her former government.
In the letter she said she planned a vacation with her son, Supasek Amornchat, in Europe from July 21 to Aug 10.
Observers expect Ms Yingluck to also attend a 65th birthday party for her elder brother and former prime minister Thaksin Shinawatra in France on July 26.
Since early this month many key figures of Ms Yingluck's Pheu Thai Party have requested permission from the NCPO to leave the country.
A source in the NCPO said Gen Prayuth was likely to approve Ms Yingluck's request because notice of her plans had earlier been given informally and Gen Prayuth had given verbal approval. That led to her written and official request.
Ms Yingluck was required to report her movements during her overseas trip. She also planned to visit England, the source said.
A source close to Ms Yingluck said that she would return to Thailand. Her flight is scheduled to depart early Monday morning.
NCPO spokesman Col Winthai Suvaree said on Thursday that Ms Yingluck was complying with the NCPO's previous request for her cooperation. The NCPO did not overly limit people's rights and was focusing on seeking cooperation.
Ms Yingluck had not resisted any instructions or peace-keeping efforts, so the NCPO did not reject her request, Col Winthai said.