Thanks guys. It does indeed run on gas, LPG, which Thailand has a lot of up in the Northeast. These are two-stroke engines with oil injection and they sound like machine guns when they're running.
They are used for preparing the soil for the next rice crop. In the part of Thailand where the photo was taken this morning, some farmers get three crops per year, and all kinds of technology is used to speed up the process. Here's the next step, leveling the paddy field:
D300 with 70-300 ED @ 220mm and f/8