As mentioned in the Bionic Beaver release notes, Ubuntu 18.04 LTS will not have a 32 bit Desktop Image Installer. But in the beta 1 release it has 32bit Desktop Images.
This is little off topic, but I'm confused.
If you want a 'clean and basic' iso file of Ubuntu Bionic to be released as 18.04 LTS, you can download a Ubuntu mini.iso alias Netboot iso file. There are versions for 32-bit as well as 64-bit kernels.
During the development phase (until April 2018) you will find the Bionic mini.iso files
You will find more details and the released mini.iso files via this link,
mini.iso, minimal install, netboot iso
You can use the mini.iso to install standard Ubuntu as well as the community flavours of Ubuntu. You can also create an Ubuntu Server or a custom system with only some manually selected program packages.
But Ubuntu Desktop (standard Ubuntu) and Ubuntu Server 18.04 LTS will only be released with 64-bit iso files (for standard PC computers) as described in the answer by @pomsky.
