Piukala has been appointed to help raise awareness of the issues and experiences of non-communicable diseases in the Pacific.
Singaporean Minister for Health Gan Kim Yong was appointed in his personal capacity to the commission in February.
The two join 18 other commissioners representing various countries and non-governmental health organisations.
Launched by WHO director-general Dr Tedros Adhanom Ghebreyesus, the commission will propose bold and innovative solutions to accelerate prevention and control of diseases such as heart disease, stroke, diabetes and cancer.
The western Pacific has some of the highest rates of NCDs, with cardiovascular and chronic respiratory diseases, diabetes and cancers alone accounting for more than eight out of 10 deaths in the region. Many of these are premature and preventable.
Tonga is no exception with recent statistics highlighting that approximately one in five Tongans have diabetes.
Despite having taken some positive steps, much more needs to be done to reduce the burden of NCDs in Tonga, according to Piukala.
"These are avoidable diseases," he said.
"This is why we have developed and are implementing a national strategy for combatting NCDs, which localises global guidelines and sets forth realistic, achievable actions for our entire community.
"In Tonga, some of the biggest drivers of this crisis are unhealthy diets and lack of physical activity.
"We need innovative ways to protect people from tobacco, change behaviours and provide our communities with safer, healthier options."