This monument was erected to the glory of King Rama I, first king of the dynasty of the current King of Thailand. It stands in the middle of a huge roundabout. In the center, there is a pedestal with an elephant ridden by soldiers symbolizing the victorious battles led by the Siamese army (at the time, the country was still called the Kingdom of Siam).
There are also since 2020, 9-storey parasols arranged all around the statue which at night when they are lit really give a magical atmosphère to the place. So I really advise you to go there at nightfall.