The subject invention comprises a thin lamp assembly having a lens and a lamp housing heat staked and sealed together. The subject invention further comprises the method of assembling the thin lamp assembly. In one embodiment, the lens has a plurality of plastic stakes and a lens rib located around the lens' periphery. Further, the lamp housing has a plurality of receiving holes around its outer periphery and a lamp housing rib around its inner periphery. In this embodiment, a sealant is placed on the lamp housing and the plastic stakes are inserted into the receiving holes so that the lens rib and lamp housing rib form a seal channel to contain the sealant and the lens is flush with the lamp housing. A heat source is then used to heat treat the plastic stakes to form a plurality of mushroom caps that act to attach the lens to the lamp housing.