The man was identified as Rungroj Sathienpreecha, a resident of Mueang Pathum Thani district.
A municipality official, Saengduan Jakhongsa told police that she spotted something falling from above while she was having lunch with friends on the ninth floor.
When she looked down, she saw the body on the ground.
A life insurance policy and a note of underground lottery bidding were found on his body.