Let’s get the important warning out of the way before you book any plane tickets – you must not carry Cannabis you’ve bought in Thailand on international flights. This is a very good way to end up in jail.
This is true even if the destination country is one where pot has been decriminalized. The Dutch may not mind possession for personal use, but they really do mind drug smugglers. Don’t do it.
Quick Summary: Yes, you can carry cannabis on a domestic flight but it must be in your hold luggage, not your hand luggage.
Can I Carry Cannabis On A Domestic Flight In Thailand?

There is no firm legal guidance on this issue, as yet. As you may, or may not, know the full legislative agenda for cannabis in Thailand has not fully rolled out – so, this advice may change and if it does, we’ll update it.
But for now, there is no law against possessing cannabis on a flight within Thailand but the aviation authority, Airports of Thailand (AOT), sets rules for flying in the country and they do offer some guidance.
They say that if you want to bring legal cannabis or legal cannabis products onto a flight that will operate entirely in Thailand, you should pack it into your checked baggage and not try to carry it onto the plane in your hand baggage.
This isn’t AOT being arbitrary or capricious, The Office of Narcotics Control Board is required to inspect all hand luggage containing cannabis. Worse, they may also seize the cannabis and then assay it to ensure it’s under the legal levels of THC.
Given that quality control in Thailand’s nascent cannabis industry is a relatively new thing, you might not want to presume that your recent purchases in a dispensary are within legal limits. So, checking your pot and pot products in the hold is best.
You may also bring cannabis plants and flowers onto the plane for a domestic flight but again, you should pack these into checked baggage (which will require some care as baggage handlers won’t give your bags special treatment because they have plants inside).
It is also OK to bring any cannabis extract in your checked luggage though this must be under the 0.2% THC threshold.
What Happens If I Try To Take Cannabis On A Thai Domestic Flight In My Hand Luggage?

You get stopped at security. They call an officer from the Office of Narcotics Control Board. That officer will search your luggage again.
They may, or may not, then confiscate any products for further testing to ensure their legality. You may be required to wait while this testing is completed.
This means, you may not be able to catch your flight and you would need to pay for a new flight ticket.
So, if you only travel with hand luggage our advice would be to use up what you have before heading to the airport and then buy some more when you land – there are dispensaries everywhere in the country now.