Causes of Reincarnation If Buddha didn't believe in soul why did he believe in Re-incarnation, after life etc which could be because of soul ? What causes one to be born again, is that the desire, if it's the desire, Buddh's belief is the same as told by Krishna(who is supposed to be the previous incarnation of Buddha) who said "what you think at think about at the time of dying, you will be born likewise" Is the desire main cause of "Re incarnation" ?
The Pali scriptures (e.g. SN 12.2) define the word 'jati' ('birth') to mean the mental generation of the view, idea or thought concept of 'beings' ('satta') or 'self'. Please also refer to SN 5.10.

For example, in India today, the word 'jati' means 'social-self identity' or 'caste' rather than child birth from a woman's womb. To quote Wikipedia:


  Jāti (in Devanagari: जाति, Bengali: জাতি, Telugu:జాతి, Kannada:ಜಾತಿ, Malayalam: ജാതി, Tamil:ஜாதி, literally "birth") is a group of clans,
  tribes, communities and sub-communities, and religions in India. Each
  jāti typically has an association with a traditional job function or
  tribe. Religious beliefs (e.g. Sri Vaishnavism or Veera Shaivism) or
  linguistic groupings may define some jatis. Among the
  Muslims, the equivalent category is Qom or Biradri.
  
  A person's surname typically reflects a community (jati) association: thus Gandhi = perfume seller, Dhobi = washerman, Srivastava = military
  scribe, etc. In any given location in India 500 or more jatis may
  co-exist, although the exact composition will differ from district to
  district.


This contemporary Indian meaning of the word 'jati' is also found in ancient Pali scriptures, such as MN 98 (which describes the various social designations or 'jati' of people based on their kamma) and MN 86 (which refers to the life of a monk as a 'noble birth'). 

Therefore, what is called 'rebirth' in the Pali scriptures is the re-arising of this 'self-view' or 'self-social identity' within the mind (rather than reincarnation from life-to-life). 

This 'rebirth' is caused ignorance &amp; craving. Due to kamma (action), the mind develops more craving &amp;, due to ignorance, the mind clings to that craving as 'self' or 'me'. This is 'rebirth'. 

The famous Buddhist monk Ajahn Sumedho said: 


  Or, we speculate about re-birth: what is it that carries on from one life to the next if there's no soul? If everything's anatta, how can
  'I' have been something in a previous life and have some essence that
  is born again?
  
  But if you watch the way things operate independently of yourself, you begin to understand that rebirth is nothing more than desire
  seeking some object to absorb into, which will allow it to arise
  again. This is the habit of the heedless mind. When you get hungry,
  because of the way you've been conditioned, you go out and get
  something to eat. Now that's an actual rebirth: seeking something,
  being absorbed into that very thing itself. Rebirth is going on
  throughout the day and night, because when you get tired of being
  reborn you annihilate yourself in sleep. There's nothing more to it
  than that. It's what you can see. It's not a theory, but a way of
  examining and observing kammic actions.
  
  Kamma &amp; Rebirth


As for Krishna, his appearance in the Bhagavada Gita (composed around 200 BC) occurred after the Buddha therefore Krishna could not be a previous reincarnation of the Buddha. Such ideas are obvious Hindu rather than Buddhist because, in the Pali Buddhist scriptures, the only gods mentioned are Indra (Vishnu), Brahma &amp; Prajapati.