A source at the Department of National Parks, Wildlife and Plant Conservation (DNP) said the result should be known in two weeks.
The 10-year-old Lung Ou-an, currently being treated at the DNP Wildlife Health Division, appears to be cheerful and is eating food normally.
The 15-kilogram Lung Ou-an was captured for treatment by DNP officials last week at a park near the Khun Kala Floating Market in Bang Khun Thien.
The macaque reportedly has no symptoms of depression, although veterinarians said its health was concerning as it seemed to suffer from ascites and the abdomen tumour could be cancerous.
As it has also had been diagnosed with lung inflammation, the macaque is being given antibiotics daily and would soon have a lung X-ray.