The last time Uranus made its Aries transit, 84 years ago, Thailand's absolute monarchy was overthrown in a coup, Khaosod newspaper reported online.
Uranus is known among Thai astrologers to bring bad luck, and many predicted that its transit into Aries would bring significant changes to the country.
Many Thais are superstitious and seek advice from astrologers, fortune tellers, and mystics.
Mass prayers were held late Sunday at temples across the nation and at the Bangkok City Pillar Shrine.
The ceremonies were attended by high-ranking government officials including National Police Chief Jakthip Chaijinda and Tourism Minister Kobkarn Wattanavrangkul.
- DPA