▁The ▁old ▁Sh an ▁script ▁used ▁until ▁the ▁ 1 9 6 0 s ▁did ▁not ▁differenti ate ▁all ▁v ow els ▁and ▁di ph th ongs ▁and ▁had ▁only ▁one ▁tone ▁marker , ▁and ▁a ▁single ▁form ▁could ▁represent ▁up ▁to ▁ 1 5 ▁sounds . ▁Only ▁the ▁well - tra ined ▁were ▁able ▁to ▁read ▁Sh an . ▁This ▁has ▁been ▁fixed , ▁making ▁the ▁modern ▁Sh an ▁alphabet ▁easy ▁to ▁read , ▁with ▁all ▁t ones ▁indicated ▁un ambigu ously . ▁The ▁standard ▁Sh an ▁script ▁is ▁an ▁ab ug ida , ▁all ▁letters ▁having ▁an ▁inher ent ▁v owel ▁a . ▁V ow els ▁are ▁represented ▁in ▁the ▁form ▁of ▁dia crit ics ▁placed ▁around ▁the ▁con son ants . ▁ ▁The ▁Sh an ▁alphabet ▁is ▁much ▁less ▁complex ▁than ▁the ▁Th ai ▁one ▁and ▁la cks ▁the ▁not ions ▁of ▁high - class , ▁mid - class ▁and ▁low - class ▁con son ants , ▁dist in ctions ▁which ▁help ▁the ▁Th ai ▁alphabet ▁to ▁number ▁some ▁ 4 4 ▁con son ants . ▁Sh an ▁has ▁only ▁ 1 9 ▁con son ants , ▁and ▁all ▁t ones ▁are ▁clearly ▁indicated ▁with ▁un ambigu ous ▁t onal ▁markers ▁at ▁the ▁end ▁of ▁the ▁sy ll able ▁( in ▁the ▁absence ▁of ▁any ▁marker , ▁the ▁default ▁is ▁the ▁rising ▁tone ). ▁ ▁The ▁number ▁of ▁con son ants ▁in ▁a ▁text book ▁may ▁vary : ▁there ▁are ▁ 1 9 ▁univers ally ▁accepted ▁Sh an ▁con son