The finance and securities sector index fell 2.52 percent at 1,475.93 points, while banking lost 1.58 percent at 252.35.
Energy fell 1.09 percent to close at 12,325.99 and transportation dropped 1.33 percent to 148.62.
Analyst Ekpittaya Aimkongeak from BFIT Securities highlighted Energy Minister Prommin Lertsuridej's announcement of a four percent hike from Tuesday in the price of diesel, a key transport cost, in the country's first move to wean the economy off a year-long subsidy.
Ekpittaya said investors were also concerned over other issues, including the effects of the devastating tsunamis last December and a possible rise in interest rates.
Bangkok Bank closed two baht lower at 108.00 baht and Kasikornbank closed unchanged at 57.00 baht, while Siam Commercial bank lost 0.50 baht at 50.50. Capital Nomura Securities fell two baht at 71.00, while Finansa Securities was down 1.50 baht at 27.50.
PTT Plc lost three baht at 196.00, but PTT Exploration and Production closed unchanged at 302.00.
Siam Cement and Siam City Cement both shed four baht to close at 262.00 and 274.00 respectively.
Thai Airways International was unchanged at 48.00, and Advanced Info Service was down three baht at 109.00 baht.