Guidline for Applying for Singapore VISA

http://www.mfa.gov.sg/content/mfa/consular_information/foreigners_visiting_singapore.html

Invitation Letter

Important information regarding invitation letters (please read):
The invitation letter (V39A Form) will be issued after the successful registration. 

Your name must be listed exactly as it appears on your passport. Any differences between the name on your passport and the name on your invitation letter or other documentation could lead to a delay and/or denial of your visa. 

Please note the organizing committee of the conference is not authorized to assist with the VISA process beyond providing the Invitation Letter(V39A Form). Should your application be denied, the organizing committee of the conference cannot change the decision of the Ministry of Foreign Affairs, nor will the organizing committee engage in discussion or correspondence with the MOFA or the Embassy on behalf of the applicant. The registration fee cannot be refunded when the VISA application of individual being denied. 

It takes time for the Embassy to process the VISA application, please register as early as you can to make sure you have enough time.