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
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
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 for parks and greenery 
Online feedback form for animal and bird-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
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
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