The benchmark palm oil contract for August delivery on the Bursa Malaysia Derivatives Exchange was last down 0.6pc at 2,016 ringgit ($484.38) per tonne at the midday break.
It earlier fell to 2,013 ringgit, its weakest level since May 24.
Palm oil may break a support at 2,019 ringgit per tonne and fall into a range of 1,960-1,997 ringgit, said Wang Tao, a Reuters market analyst for commodities and energy technicals.
"Palm prices are taking cue from continuous weakness in rival oilseed," said a palm oil futures trader, referring to US soyoil.
He added that the market was also cautiously trading on expectations of export data showing weaker demand in the first ten days of June.
Malaysian palm oil exports in June 1-10 period fell 31.6pc from the corresponding period in May, according to an independent inspection company AmSpec Agri Malaysia.
Slowing export demand could contribute to rising inventory levels and weigh on benchmark palm oil prices. Malaysian palm oil stockpiles last fell 6.6pc in April to 2.73 million tonnes.
Industry regulator the Malaysian Palm Oil Board is scheduled to release inventory, production and export data for May on June 12.
Meanwhile, the Chicago July soybean oil contract had declined 1.4pc on Friday, and was down again on Monday by 0.2pc.
US soy, wheat and corn prices charted declines as US farmers are expected to get a window of dry weather this week for planting activity.
In other related oils, the September soyoil contract on the Dalian Commodity Exchange rose 0.4pc, and the Dalian September palm oil contract edged up 0.1pc.
Palm oil prices are affected by movements in related edible oils, with which it competes for global market share.