Santo Tomas comprises 27 barangays with an estimated population of 18,365. 23 of its barangays (85%) are connectivity dead zones with no recorded cell tower from either the national registry or crowdsourced data.
| Barangay | Population | Towers | Coverage |
|---|---|---|---|
| Ammugauan | 961 | 0 | Dead zone: no towers from any source |
| Antagan | 557 | 0 | Dead zone: no towers from any source |
| Bagabag | 399 | 0 | Dead zone: no towers from any source |
| Bagutari | 796 | 0 | Dead zone: no towers from any source |
| Balelleng | 817 | 2 | Crowdsourced signal only (no registered tower) |
| Barumbong | 1,056 | 0 | Dead zone: no towers from any source |
| Biga Occidental | 303 | 0 | Dead zone: no towers from any source |
| Biga Oriental | 497 | 0 | Dead zone: no towers from any source |
| Bolinao-Culalabo | 801 | 0 | Dead zone: no towers from any source |
| Bubug | 780 | 0 | Dead zone: no towers from any source |
| Calanigan Norte | 163 | 0 | Dead zone: no towers from any source |
| Calanigan Sur | 399 | 0 | Dead zone: no towers from any source |
| Calinaoan Centro | 502 | 4 | Crowdsourced signal only (no registered tower) |
| Calinaoan Malasin | 75 | 0 | Dead zone: no towers from any source |
| Calinaoan Norte | 79 | 1 | Crowdsourced signal only (no registered tower) |
| Cañogan Abajo Norte | 965 | 0 | Dead zone: no towers from any source |
| Cañogan Abajo Sur | 1,301 | 0 | Dead zone: no towers from any source |
| Cañogan Alto | 1,381 | 0 | Dead zone: no towers from any source |
| Centro | 1,123 | 0 | Dead zone: no towers from any source |
| Colunguan | 548 | 1 | Crowdsourced signal only (no registered tower) |
| Malapagay | 287 | 0 | Dead zone: no towers from any source |
| San Rafael Abajo | 640 | 0 | Dead zone: no towers from any source |
| San Rafael Alto | 502 | 0 | Dead zone: no towers from any source |
| San Roque | 1,160 | 0 | Dead zone: no towers from any source |
| San Vicente | 635 | 0 | Dead zone: no towers from any source |
| Uauang-Galicia | 625 | 0 | Dead zone: no towers from any source |
| Uauang-Tuliao | 1,013 | 0 | Dead zone: no towers from any source |