What should we do when there is a difference in determining the beginning and end of the month of Ramadan between the Chinese Islamic Association, which adopts thirty days for each lunar month, the Kingdom of Saudi Arabia, and our home countries?

You must rely on the sighting of the Ramadan (definition) crescent in your country and nearby countries that share the same moonrise (matla') with you. If you do not sight it, then it is obligatory to complete Sha'ban as thirty days. Do not rely on the sighting in Saudi Arabia or distant countries due to the difference in moonrises (matali'), nor on the aforementioned society if it does not rely on the sighting of the crescent.