The king's endorsement was needed before the election could go ahead within a mandatory 60 days of a royal decree, according to the constitution. The decree will take effect on Aug. 24, said Rongphon.
Thailand held a general election on April 2, three years ahead of schedule, but it was boycotted by the three parliamentary opposition parties. The nation's top court's later nullified the April poll, calling it undemocratic and unconstitutional after it was criticized by the king, according to the AP.
Since parliament was dissolved in February, Thailand has had no working legislature and only a caretaker government under Prime Minister Thaksin Shinawatra.
A drone video shows a Russian flag flying over the outermost house in the west of the city.