The Jakarta Post showed the number of gold medals won by Indonesian during the recent SEA Games. They won 45 gold medals at the 2015 games in Singapore. But in 2011, when the SEA games were held in Palembang, Indonesia they won over 200 gold medals.
It seems that the host country usually wins more gold medals than usual. I was told that the host country could decide on the games to be played, and they chose the games where they are expected to do well.