This is what they can be looking at as punishment.
For Cannabis Under Category 5:
From 2-15 years imprisonment and a fine of 200,000 – 1,500,000 Baht for production, importation or exportation
From 2-10 years imprisonment or a fine of 40,000 – 200,000 Baht or both for disposal or possession for the purpose of disposal. If the quantity is over 10 kilograms, the penalty is increased to a maximum of 15 years and a fine of 200,000 – 1,500,000 Baht
Imprisonment not exceeding 5 years and or a fine not exceeding 100,000 Baht or both for possession
Imprisonment not exceeding 1 year and a fine of 100,000 – 1,000,000 for consumption