Generally speaking, bitmap pictures (for example PNG graphics) images can be used as textures for 3D objects (.obj). So any program capable of this operation can perform this can of "conversion", although it's more of a workflow than conversion really.
Convert Portable Network Graphic to 3D object graphics.
We have found 8 software records in our database eligible for .png to .obj file format conversion.
Microsoft Windows software - convert png to obj on Windows
A 3D CAD translation softwate
Convert from png file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned png to obj. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A texture mapping utility
A graphics design tool for making 3D landscaping and animations
PMD, PMX, X MikuMikuDance model editor
A 3D general-purpose modeling program
An application for the planning of spaces and furnishings
Apple macOS / Mac OS X software - convert png to obj on OS X
3D modeling and animation package for Mac.
3D modeling application for Mac