Depends on the furniture application. If the furniture is bound to get exposed to steam or water regularly, go for Marine Grade Ply (Ask for I.S. 710 specification ). If not, such as cabinets or cupboards, you could opt for a cheaper, BWR Grade ply (I.S - 303) or even MR Grade ply if you’re putting on laminates on the whole lot.
Apart from the grade you should be looking at the timber species used in making the plywood before purchasing as well. For sturdy and long lasting furniture, always go with hardwood timber made plywood. Of the many species, the most widely used timber in Indian plywood industry is Eucalyptus & Gurjan. Eucalyptus is domestically cultivated and a sustainable source while Gurjan is the most expensive, imported and unsustainable source. Your choice.
For lighter usage furniture, you could opt for cheaper sapwood timber such as Poplar timber made plywood. Its distinguishable by its complete white core color. Its also probably the cheapest plywood you would get in the market without compromising the structural integrity of the ply. Do NOT go for rubberwood made plywood made in Kerala. Would be a disaster.