Thailand shipped 85,816 tonnes or 30.4 per cent during the January-August period of this year to Singapore, reported The Straits Times today.
Vietnam supplied 77,459 tonnes or 27.4 per cent of rice supply during the period.
Indian rice exports to Singapore had risen to 29.5 per cent last year from 15.3 per cent in 2009.
Thailand has been the leading rice supplier to Singapore since 1998, accounting for over half of the total rice consumption of the city state between 1998 and 2011.
But its market share fell to 35.3 per cent last year while supplies from India and other countries have increased.
"Importers (are) taking advantage of the lower prices of Indian rice compared to Thai rice," the daily quoted a Trade and Industry Ministry spokesman.
The Singapore General Rice Importers Association said the shift in sourcing rice started when global rice prices began surging in 2008.
Other rice producing countries have also curbed exports to ensure sufficient domestic supplies while Thai crops have been hit by massive floods in the past.
Other rice suppliers to Singapore include Myanmar (2.5 per cent), Pakistan (2.4 per cent), the United States (2.2 per cent), Cambodia (0.9 per cent) and Australia (0.6 per cent) as well as others (0.7 per cent).