<p>In this study, the effects of fungicides were evaluated for their fungicidal activities against rice seedling rot, brown spot, and false smut diseases under field conditions in Thailand. The results showed that rice seeds treated with carbendazim + mancozeb displayed the most effectiveness in controlling rice seedling rot disease, causing up to 73.09% disease reduction. Two applications of all fungicides showed more effectiveness against rice brown spot disease than one application. The combined fungicides, propiconazole + azoxystrobin, showed superior effectiveness in reducing brown spot disease incidence by up to 75.12%, while two applications of azoxystrobin, edifenphos, propiconazole, and tebuconazole were not significantly different to each other, causing 60–65% disease reduction. Meanwhile, two applications of difenoconazole + propiconazole were the most effective in controlling the false smut disease, with 69.16% disease reduction over the control treatments. Moreover, azoxystrobin, carbendazim, and propiconazole showed moderate fungicidal effects against false smut disease, causing 50–60% disease reduction. Rice yields in all fungicidal treatments were significantly higher than in the control. The maximum yield increases were found with the treatment of difenoconazole + propiconazole, increasing rice yield by 27.06%, followed by propiconazole and azoxystrobin, which increased yield by 21.63% and 20.25%, respectively, over the control treatment.</p>