An underwhelmed Morales said the aid from the most industrialized countries was part of the world's "obligation" to preserve the Amazon rainforest.
"I welcome that small, small, tiny contribution of USD 20 million from the G7 -- that is not help, it is part of a shared co-responsibility, as all peoples have the obligation to preserve the ecosystem," Morales told Bolivia's Radio Panamericana.
The richest nations "should contribute a lot, and not only when there are fires," the president said, adding that he hoped the aid would arrive as quickly as possible.
Bolivia is one of nine South American countries to share the Amazon rainforest.
While fires in Brazil have captured the world's attention, Bolivia has been fighting its own blazes that Morales said Tuesday had destroyed 1.2 million hectares, or more than 4,000 square miles of forest and grassland, since May.
Bolivia has enlisted a Boeing 747 "Supertanker" from the US to bolster its effort to quench the fires from the air.
Morales told the radio he had agreed with Paraguay's President Mario Abdo to allow fire-fighting aircraft to cross one another's border wherever necessary to fight the fires.
G7 countries meeting in France made the USD 20 million aid offer to help Brazil and Bolivia fight the blazes.
Brazil rejected the offer amid a spat between President Jair Bolsonaro and his French counterpart Emmanuel Macron, who has blamed his policies for damaging the Amazon.
Like Bolsonaro, Morales has been criticized for his land-clearing policies. On Tuesday, he said he had decreed a pause in land sales and purchases to prevent people taking advantage of the fires clearing large areas of land for crops and livestock.