I remember seeing these scooters in Thailand 2003 and being facinated by them. An evolved, over customised, skinny wheeled, with or without plastics child of the Honda C90.
Wikipedia:
An underbone is a small motorcycle built on a frame consisting mostly of one large diameter tubular component. The stylistic difference between a motorcycle and an underbone is considerable and they are sometimes known as "step-throughs" or even marketed as scooters in the West.
The fuel tank position and the open-frame design, along with the splash guards often fitted, give the underbone an appearance similar to ascooter, however the wheels, engine position, and power transmission are based on the design of conventional motorcycles.
Underbones are popular worldwide, but in East Asian and South East Asian countries in particular they dominate the low cost market segment with their scooter-like ease of use, their appeal to both sexes, and their motorcycle-like dependable handling properties.
KUSTOM Anodize
Delicate, Spindly bicycle tyres/wheels, Plastics. Built for speed.
AnodizeZIPPPPPPPPPPPs
BlackZIPPPPPPPPPPPPPs
Malaysian HIGH-LOW TECH MONO
Bikes look better on Mats
Rims
Underbone Drag. Strip plastics. Anodize. Suzuki 175. Rebel Denim Look.
Stretch and Strip-very heavy look but a bit silly too.
Bottle Tank
Anodize mix
Extreme Cal Look
Subtle Cal Look
Very Sick DRILLED hubbed C90
British Farm Style
Koh Pha-Ngan Style Bike and Foot. Sick. Drilled swing arm weight reduction.