Siasi, officially the Municipality of Siasi, is a 2nd class municipality in the province of Sulu, Philippines. According to the 2020 census, it has a …Siasi, officially the Municipality of Siasi, is a 2nd class municipality in the province of Sulu, Philippines. According to the 2020 census, it has a population of 81,689 people. Siasi is politically subdivided into 50 barangays. Each barangay consists of puroks while some have sitios.