How large is the 72-hour transit visa

German Passport holder, I have two questions: I would like to fly from Thailand (BKK) to Shanghai, make use of the 3 day policy and then fly out to Malaysia or Singapore. Would this work or are the destinations too close to each other (same region) ? Also, do you know how much space in the Passport is needed, e.g. if a full page is needed for the 3 day transit permit or if it is just a stamp? My passport has only little empty pages left. Thanks for your answer in advance. Lukas
Also if it is OK that I am using different airlines, not sure how much of an requirement this might be.