What is meant by thought in the spiritual parlance is a vibration of light that originates in the Light of the Divine and the descends through several layers where it gets clothed in varying degrees of ignorance. As it enters the human mind it assumes the covering and colouring of our ignorant mind and wears the costume of language and speech to which one is attuned to and conditioned.
Our state of consciousness acts like a trigger to open the channel of Thought vibrations attracting the corresponding level of thought much like a remote displays the program on the TV that it chooses. Once it enters the brain it automatically picks up the dress of language, again just as one can by changing the channel watch the same program in a regional or national language. Important thing is the state of our consciousness and the level to which we open either through habit or conscious aspiration, meditation and concentration. The rest is automatic like the selection of the language and the nature of the program.
Affectionately,
Alok Da