Can I add a 16GB SODIMM to a laptop with 16GB soldered RAM?

Yes, adding a single 16GB SODIMM to a laptop with 16GB soldered will give you 32GB total—assuming the slot supports it. Most modern laptops with soldered RAM plus one SODIMM slot are designed for this exact upgrade path. But check your model’s max RAM support and BIOS restrictions, as some laptops limit the SODIMM slot or require matching capacities.