  We consider the di-photon signal arises from two bunches of collimated photon
jets emitting from a pair of highly boosted scalars. Following the discussion
of detecting the photon jets at the collider, we extend the two-Higgs-doublet
model (2HDM) by adding a gauge singlet scalar. To explain the di-photon excess
which is recently observed at the first 13 TeV run of the LHC, the mixing
between the heavy doublet state and the newly added singlet is crucially
needed. After the mixing, one can have a heavy Higgs state $Y_2$ at 750 GeV and
a very singlet-like scalar $Y_1$ of sub-GeV, which would be highly boosted
through the $Y_2$ decay. Both real singlet and complex singlet extension are
studied. It turns out that only the complex model can yield the 1-10 fb cross
section in the di-photon final state in accompany with the decay length of the
order of 1 m for the $Y_1$. This complex model parametrically predicts the
width of 750 GeV resonance $\gtrsim 1$ GeV. In addition, the pseudoscalar
component of the singlet in this model is naturally stable and hence could be a
dark matter candidate.
