There are 18 words that start with 'thia'.
| thiamin | thiazin |
| thiazol | thiamine |
| thiamins | thiazide |
| thiazine | thiazins |
| thiazole | thiazols |
| thiamines | thiazides |
| thiazines | thiazoles |
| thiaminase | thiaminases |
| thiabendazole | thiabendazoles |
Note: These 18 words that start with 'thia' are found from the USA & Canada version of the tournament Scrabble word list.