Siay comprises 29 barangays with an estimated population of 62,492. 18 of its barangays (62%) are connectivity dead zones with no recorded cell tower from either the national registry or crowdsourced data.
| Barangay | Population | Towers | Coverage |
|---|---|---|---|
| Bagong Silang | 795 | 0 | Dead zone: no towers from any source |
| Balagon | 6,193 | 0 | Dead zone: no towers from any source |
| Balingasan | 766 | 0 | Dead zone: no towers from any source |
| Balucanan | 1,713 | 0 | Dead zone: no towers from any source |
| Bataan | 731 | 0 | Dead zone: no towers from any source |
| Batu | 2,603 | 1 | Crowdsourced signal only (no registered tower) |
| Buyogan | 3,710 | 0 | Dead zone: no towers from any source |
| Camanga | 1,251 | 0 | Dead zone: no towers from any source |
| Coloran | 5,411 | 2 | Crowdsourced signal only (no registered tower) |
| Kimos (Kima) | 1,315 | 5 | Crowdsourced signal only (no registered tower) |
| Labasan | 1,024 | 1 | Crowdsourced signal only (no registered tower) |
| Lagting | 1,307 | 0 | Dead zone: no towers from any source |
| Laih | 1,706 | 1 | Crowdsourced signal only (no registered tower) |
| Logpond | 5,975 | 3 | Crowdsourced signal only (no registered tower) |
| Magsaysay | 1,473 | 0 | Dead zone: no towers from any source |
| Mahayahay | 1,793 | 0 | Dead zone: no towers from any source |
| Maligaya | 477 | 0 | Dead zone: no towers from any source |
| Maniha | 1,146 | 0 | Dead zone: no towers from any source |
| Minsulao | 1,574 | 0 | Dead zone: no towers from any source |
| Mirangan | 1,626 | 2 | Crowdsourced signal only (no registered tower) |
| Monching | 7,904 | 8 | Crowdsourced signal only (no registered tower) |
| Paruk | 1,763 | 0 | Dead zone: no towers from any source |
| Poblacion | 622 | 1 | Crowdsourced signal only (no registered tower) |
| Princesa Sumama | 569 | 0 | Dead zone: no towers from any source |
| Salinding | 1,319 | 2 | Crowdsourced signal only (no registered tower) |
| San Isidro | 770 | 0 | Dead zone: no towers from any source |
| Sibuguey | 1,807 | 0 | Dead zone: no towers from any source |
| Siloh | 4,751 | 2 | Crowdsourced signal only (no registered tower) |
| Villagracia | 398 | 0 | Dead zone: no towers from any source |