With $40 aluminium rigid fork and some quality parts, you can easily make this bike ~10kg without spending too much. It is still large, but actually lighter than most folding bikes at similiar price range. I occasionally carry the bike on the bus and bus drivers usually let me in.

I'm now working on fitting lightweight components AND 700c road wheelset to hummer frame. Current build plan includes SRAM rival drivetrain, some lightweight parts(3T Prima 199 handelbar, F99 stem, KCNC seatpost, am classic wheelset). From my spreadsheet, it'll turn into a 8.5kg (w/o pedals) foldable road bike.