The manga doesn't differentiate between telepathy and thinking something except when there is screaming like when Nausicaä hear the Ohmu scream [1] or the insects scream [2].
Mito and Nausicaä seem to have a two-way exchange after Kushana's brief invasion of the Valley [3].
Nausicaä 'shouts' to Asbel during his his attack [4].
Nausicaä speaks with the Holy One using telepathy [5].
Other possible psychic moments, but not sure: Nausicaä trying to calm Teto [6], Rastel in her last moments with Nausicaä [7], and Yupa to Nausicaä during the duel [8].
References[]
a See Page Conversions Between Editions to convert Deluxe Edition volume 1 (DE1) to other editions