The Royal Gazette on Tuesday published an announcement on the royally-approved list of 250 senators, including 66 army generals.
The announcement dated on Saturday included Gen Preecha Chan-o-cha, younger brother of Prime Minister Prayut Chan-o-cha, Adm Sitthawat Wongsuwon, younger brother of Deputy Prime Minister and Defence Minister Prawit Wongsuwon, Klanarong Chantik, former secretary-general of the National Anti-Corruption Commission (NACC), former deputy prime minister Chatchai Sarikulya, former national reform member Khamnoon Sitthisaman, former foreign trade director-general Duangporn Rodphaya, and former national security council secretary-general Thawil Pliensri.
Among other senators were Pornpetch Wichitcholchai, former president of the National Legislative Assembly, former NACC chairman Panthep Klanarongran, forensic expert Khunying Porntip Rojanasunan, former deputy agriculture minister Luck Wajananawat, and former tourism and sports minister Weerasak Kowsurat.
More than a third of the newly appointed senators have military or police backgrounds, a sign the upper house will probably vote to entrench army dominance of government five years after a military coup.
"There is no denying that the Upper House will be a tool to extend the junta's power," said Piyabutr Saengkanokkul of the Future Forward Party, which opposes military rule.
But the Senate may be the key to keeping Gen Prayut in power, as it will vote in a combined ballot with the House of Representatives to elect a new prime minister. Under previous constitutions, the House voted alone.
If all 250 senators vote the same way, Gen Prayut's party, whose allies already hold 17 seats, will have just over the majority of 376 required in the combined House-Senate vote to approve him as prime minister.
The Senate list includes the names of 105 people with ranks in the military or police, a Reuters count showed. Also among them were Gen Prayut's brother, General Preecha Chan-o-cha, and a brother of deputy junta leader Prawit Wongsuwan.
It also included 15 former ministers in Gen Prayut's cabinet who resigned last week, many of them generals counted among his close aides.
About 26 civilian lawmakers on the list also had previous ties with the junta, having been appointed as members of the rubber-stamp parliamentary body National Legislative Assembly.
Reuters could not immediately reach representatives of Gen Prayut or Palang Pracharat้ to seek comment.
Also on Tuesday the Royal Gazette published an announcement of the National Council for Peace and Order naming 50 people on the senators' reserve list as constitutionally required.
Under the 2016 charter, the 250-strong regime-appointed senate will serve a five-year term. Its first task is a joint sitting with the new house of representatives to vote for a new prime minister.
Fifty of the senators were selected from a shortlist of 200 candidates chosen in an intra-group process by various social groups and professions. Another 194 senators were chosen directly by the NCPO, and the remaining six seats were reserved for the three armed forces leaders, the supreme commander, the defence permanent secretary and the national police chief.