This is something I learned about in India and looked into before I left Thailand but there was nothing listed for them. (I have since found an independent list that has 15 Thai farms on it.) WWOOF is World Wide Opportunities on Organic Farms and by all accounts, it’s a great way to travel and volunteer while learning about farming.
So many volunteer organizations out there want you to pay to volunteer, but with WWOOF, all you pay is a membership fee of $20 a year to get access to list of farms that offer volunteering opportunities and generally with room and board. The kid I learned about it from had done it all over Australia & New Zealand…definitely a cool way to travel and see the world, that’s for sure.