Nakhon Sawan Rajanagarindra Psychiatric Hospital expects to treat an increasing number of patients because of cannabis use.
Hospital deputy director Dr Mantana Kittipeerachon said on Friday that between January and August, the hospital treated 103 patients for conditions related to cannabis use.
Of this number, 103 patients were treated as outpatients while 16 others were hospitalised.
This compares to a total of 122 cases for the whole of last year.
The recent figure indicates there will likely be a rise in the number of patients this year, Dr Mantana said.
Most patients were found to have suffered from hallucinations after using cannabis for recreational purposes, while others developed mental health conditions.
Dr Mantana said those who suffer from mental illnesses including depression, bipolar disorder and schizophrenia, as well as heart and kidney diseases, should avoid using cannabis.
Meanwhile, on Thursday, cannabis use among children was discussed at a national child and youth development seminar.
It discussed ways in which children can be better protected from the plant.
Dr Rasmon Kalayasiri, director of the Centre for Addiction Study at Chulalongkorn University's Faculty of Medicine, said society needs to adapt to recent changes in the law regarding cannabis, learn more about the plant and prevent children from accessing it.
"Children want to try new things and have easy access to cannabis products via online shopping," Dr Rasmon said.
"The effects from cannabis may have a long-term impact on their learning capabilities and mental health."