If you see a Penang Hokkien word of Hokkien origin being spelled with "ong", for example ong2 (king), kong1 (grandfather) or gong3 (stupid), you can be sure that the "ong" carries the sound /ɔŋ/. That's the same sound as of the word "king". It is also the sound of the "ong" in English, in words such as long and song, to name two. The "ong" is called a rhyme. For the same reason, you can say that long and song rhyme together.
However, as you know, Penang Hokkien borrows heavily from Malay. In Malay, the "ong" can be pronounced as /ɔŋ/ as well as /oŋ/. Words with the /ɔŋ/ sound from Malay include potong, gong (the percussion instrument), tolong, to name three. But sometimes, the "ong" is pronounced /oŋ/, as in patong, jelutong, kangkong, to name a few. To differentiate between the /ɔŋ/ and /oŋ/, many Malay words are refined to "ung", so it's often that we see patung, kangkung, belitung, spelled with "u" but pronounced with "o".
Words that come direct from Malay into Penang Hokkien are not respelled to differentiate the /ɔŋ/ from the /oŋ/ to retain the Malay spelling, if the Penang Hokkien pronunciation is the same.
About this website
Dear visitor, thank you so much for reading this page. My name is Timothy Tye and my hobby is to find out about places, write about them and share the information with you on this website. I have been writing this site since 5 January 2003. Originally (from 2003 until 2009, the site was called AsiaExplorers. I changed the name to Penang Travel Tips in 2009, even though I describe more than just Penang but everywhere I go (I often need to tell people that "Penang Travel Tips" is not just information about Penang, but information written in Penang), especially places in Malaysia and Singapore, and in all the years since 2003, I have described over 20,000 places.
While I try my best to provide you information as accurate as I can get it to be, I do apologize for any errors and for outdated information which I am unaware. Nevertheless, I hope that what I have described here will be useful to you.