I'm sure that synthetic tiger piss should work. I remember when I was a boy (about 70 years ago) we had problems with water buffalos ( the domestic Asian ones used for ploughing padi fields) that strayed into our compound. We had about an acre of banana trees and the buffalos kept destroying quite a lot of them. We tried chasing them away - a scary thing to do as they weigh close to a ton with horns longer than a man's arms - but they would stand their ground and look menacingly at us. One day, a neighbour suggested we use tiger oil derived from boiling the fat of a tiger to scare them off. To cut a long story short, the same neighbour supplied us with a small amount of the oil a few days later. He dipped 4 or 5 small pieces of rags (the size of 2x4 like the ones for cleaning gun barrels) tied to end of of short sticks which he stuck into the ground at strategic places around our banana plot, The result was hilarious....the next time a herd of around 6 buffalos ventured into the banana plot there was a mad stampede to get out after just a few minutes . That was the end of the buffalo menace. I kid you not.

Since this is a Malaysian story, all (?) Malaysians know how much monkeys, especially macaques hate 'belacan',. I wonder if pieces of belacan placed in the orchid growing area would deter the monkeys.