Sometimes also from collapsed subterranean caves with underground water :)

Although hard to generalize, tropical forests tend to have frequent rainfall. Rainfall often is acidic, with low conductivity and dissolved solids. Groundwater may be more neutral, even slightly alkaline in karst terrain, with higher conductivity and dissolved solids. Many tropical forests are low elevation, and were historically marine habitats, where limestone strata develops through time from shellfish, etc. When ocean recedes and areas exposed to rainfall, limestone weathers and as suggested, collapses or sometimes maintains underground caverns or caves. Limestone or karst groundwater will have high conductivity and dissolved solids. If the waterpools are deep, the collapsed caves are most likely, unless some other mechanism created the depression, such as meteor impact or severe erosion as an oxbow lake, mining excavation or bomb test range. A geologist or good geologic map could be helpful. Monitoring rainfall and pool/pond elevations, acidity and conductivity may be helpful in confirming data to support individual pool/pond reliance on rainfall. Connectivity to streams or rivers with periods of high water or flooding may also be a contributor In some instances.

In addition to the excellent answers above, generally speaking its both rainfall and groundwater that are water sources for water bodies inside tropical forests. Streams have high flow following rainfall, and its groundwater that contributes to baseflow in rainless periods. Ponds would be more groundwater driven, as a lot of rainfall ( wet canopy and soil moisture) goes back into the atmosphere via evapotranspiration. One could use stable isotopes of water to track sources, as long as rainfall and groundwater have different isotopic signatures.

Thank you so much Andrew Paul McKenzie Pegman William F. Hansen Amartya K Saha. Your answers are helpful to understand the pools of tropical forest.

Tropical forests have the capacity to absorb water from the ground and hold water in their bodies and release it through the root hairs, that is why even in summer months drought time water pools are still continuously supplied with water. But water pools are enhanced with water through the hydrologic cycle and I would like to catch this caption I read " No Trees, No Water, No Water, No Life."

That's very interesting. Thank you very much Merly Castronuevo Remollo