Keep your valuables in a day pack in the bus with you ALWAYS. Maybe invest in a padlock for your rucksack under the bus? We’ve travelled for three years throughout se Asia and not once had any issues at all, infact the night buses have been our preferred way to travel. Common sense prevails normally. Honestly, leaving money in a rucksack in the storage under a bus is just asking for trouble imo. Enjoy your stay in Thailand and your travels. there is FAR more good here than bad .