They had been working several days before we saw or noticed them. We first noticed the drips at the end of the stairway and the signs of wet paint. Then one day as we returned from language class and crossed the street on the overpass, there they were—two young Thai men in splattered white clothes hanging high above the busy street painting the metal railing. As we crossed, one of them looked up. I smiled at him, and he grinned back at me.

The next afternoon as we crossed over to the market, there they were again. I pulled out my camera and, using gestures, asked permission to take a picture. One of the men looked irritated and immediately returned to his work. The other smiled at me, nodded, and paused a moment to grin for the camera.

There was something about that smile that deeply appealed to my heart. It was so open and genuine. I waved my thanks. He returned my wave and returned to his painting as we continued on our way.

The next day, the painters’ work was complete, and they were gone. But the young man’s smile lingered in my memory. That man should be a Christian, I thought. I wonder if he has ever heard of Christ. I wonder if there is someone he knows who could introduce him. There are not many Christians in Bangkok, and Thailand needs many more missionaries.

I doubt I will ever see that bridge painter again, but I continue to pray for him. What an asset his open and engaging smile would be in witnessing for the One who loves him so much. But who will tell him?

• Twitter