As per my knowledge, a sin is committed when mind or body breaks the law of sages.
What does it mean by 'sinful' thoughts? What kind of thoughts are involved?
Is there an official list of these sinful thoughts?
Evil deeds, depending on how they are performed, has been classified into three groups :
1) Evil deeds performed by mind. 2) Evil deeds performed by speech. and 3) Evil deeds performed by the body.
Of which, following is the list of sinful deeds that are committed by mind or thoughts:
Manu Smriti 12.5. Coveting the property of others, thinking in one’s heart of doing harm to others , and adherence to false (doctrines), are the three kinds of (sinful) mental action
Similarly the Skanda Purana mentions the following sinful acts that involve the mind:
Adharmas or Acts of Sin are mainly of three categories: ‘Sthuula’ (in Gross Form), ‘Sukshma’ (Small in content) and ‘Athyantha Sukshma’ (Minute). These sins are performed by Mind (Manas), Tongue (Vani) or Karma (Action). The Manasik type is four-fold: Thinking of other’s women, wealth, material loss and difficulties. ‘Vachik Paap karma’ (Sinful Utterances) like lies, unpalatable sayings, blaming others and using provocative language