Few days back I made adai which came out crispy and thin. The recipie is this:

1 glass of Rice
2 spoons each of urad dal, chana dal, tur dal and you can also add moongdal
Red chillies according to your taste
Hing Powder
Kadi patha
salt to taste

Grind the above very fine just as you grind for dosa. The batter should not be very thick . While making adai I made it with butter instead of til oil. The adai came out crispy. The usual adai we make usually people make it thick.