Slash and burn in the Laotian countryside. Marielle Descalsota/Insider I traveled to Laos to experience its new China-made railway. The one-hour trip revealed a countryside that's burned from farming. The air was so toxic that soot and ash were falling from the sky. Laos is one of the few remaining communist countries in the world. Some two-thirds of Laotians still live in rural communities. But a shiny new railway funded by China now cuts through the countryside. The train's driver's cab. Marielle Descalsota/Insider The Laos-China Railway is the biggest infrastructure project in the history of Laos. It's a massive 1,000-kilometer,…