Radhekrishna,
As per Sanskrit Thotaka Mangalam is correct, but i asked many eminent bhagavathas they also said Thotaka Mangalam is correct, but while singing or discussing with others they will also spell it as Thodaya mangalam. In Bhajana Sampradhaayam book also lot of mistakes,Main thing is we should see the lyrics then raagam now a days it is vise-a-versa, the purpose will be defeated.
Its my humble request especially to who attached to thennangur ashram or GAT pls spell it as Thotaka Mangalam.
Radhekrishna
Balaji.M
Bangalore
--
Radhekrishna
Balaji