The magnet lattice for the Slam Photon Source, the first storage ring
for synchrotron radiation research in Thailand, has been designed. The
storage ring has a double-bend achromat lattice and fourfold symmetry
with four straight sections. Although the magnet lattice is relaxed,
an emittance value of 72 pi nm rad has been obtained, which is only 1.
4 times as large as the theoretical minimum emittance with eight bendi
ng magnets. The dynamic aperture is found to be much larger than the p
hysical aperture.