You can direct your query to the relevant Statutory Board: 

Building and Construction Authority
Tel: 1800 342 5222 (weekdays: 8.30am to 12.30pm and 1.30pm to 5.00pm; excluding public holidays) 
Online feedback form: https://www.bca.gov.sg/feedbackform/
For more information, please refer to https://www1.bca.gov.sg/contact-us  

Housing & Development Board
Tel: 6490 1111 (weekdays: 8.30am to 5.00pm)
Online feedback form: http://www.hdb.gov.sg/feedback 
For more information, please refer to https://www.hdb.gov.sg/contact-us

National Parks Board
Tel: 1800 471 7300 / 1800-476 1600 (Animal Response Centre)
Online feedback form: https://www.nparks.gov.sg/feedback (for parks, greenery and animal-related matters) and https://www.avs.gov.sg/feedback (for dog licensing and animal-related matters)
For more information, please refer to https://www.nparks.gov.sg/contact-us

Urban Redevelopment Authority
Tel: 6221 6666 / 1800 221 2616
Online feedback form: https://www.ura.gov.sg/feedbackWeb/contactus_feedback.jsp 
For more information, please refer to https://www.ura.gov.sg/Corporate/Contact-Us    

Council of Estate Agents
CEA Customer Service hotline: 1800 643 2555
For more information, please refer to https://www.cea.gov.sg/  

Board of Architects Singapore
Tel: 6222 5295
Email: board@singnet.com.sg 
For more information, please refer to http://www.boa.gov.sg/  

Professional Engineers Board Singapore
Tel: 6334 2310
Email: registrar@peb.gov.sg
For more information, please refer to https://www.peb.gov.sg/contactus.aspx  

Strata Titles Board
Tel: 6325 1589
Online feedback form: https://www.stratatb.gov.sg/feedback.html 
Email: mnd_strata_titles_boards_enquiry@mnd.gov.sg 
For more information, please refer to https://www.stratatb.gov.sg/contact-us.html 

Alternatively, you can contact the Ministry at:
Tel: 6222-1211
Fax: 6325-7254
Email: mnd_hq@mnd.gov.sg