Was on that bus some days ago, shortly after the immigration complex in Pagang Besar loads of blue plastic containers were loaded in the hold of the bus, must have been 20-30 50liter or so square blue containers. The smell of gasoline was pungent, even in the passenger cabin with all windows open. You don't need to have a Phd. in Chemistry to know that the vapors in the hold could go up to the saturation point at which any spark could mean desaster, let alone when any accident happens.

Very bad criminals to put the lives of passengers and others at risk for their own good.

This has been going on for years, nothing too much to worry about.

Most of those buses keep their doors open so the fumes smell strong to us but aren't in much danger of igniting.

If you're worried about your next trip, take the minibus for 80 baht. Yes, it means walking into town (5 mins) but you'll have peace of mind instead of becoming a piece of BBQd meat.