How can I get a Tibet Traveling Permit in Singapore without booking through tour?

It is hard to get a Tibet Entry Permit if you don't join a tour group because Tibet prohibit individual tourists to travel to Tibet.

You can try to get a Tibet Entry Permit in this way:
1. contact a travel agency in China to help you to obtain a Tibet Entry Permit without joing its tour group
2. when you apply for a China tourist visa in Singapore, don't mention that you will go to Tibet on the visa application form, otherwise, you will be asked to provide Tibet Entry Permit when you apply for China visa.
Once you obtain a valid China visa, then go to a city, such as Beijing, Shanghai, Xian and contact the travel agency to mail the Tibet Entry Permit to you,
3. then you can visit Tibet by holding a valid China visa and Tibet Entry Permit.