In this letter, a flexible and ultra-thin uniplanar end fire antenna employing spoof surface plasmon polariton (SSPP) is proposed. The single-metal layered groundless structure is an inherent advantage of the SSPP. At the SSPP transmission line's end, a metallic strip is added asymmetrically for wideband radiation, resulting in an observed tilting of the main lobe in the azimuthal plane. Three C-shaped directors are used to enhance the directivity. The proposed antenna is fabricated and measured over flat and curved surfaces of brick wall and wood with two different radii. The proposed antenna has a low profile of 0.001710 and a small volume of 0.0058?(3)(0), where 10 is the free-space wavelength at the center frequency of the operating bandwidth. The antenna has an impedance bandwidth of 33.7% with a peak gain of 8.5 dBi. Measurements indicate no significant degradation in the proposed antenna's performance in different scenarios. Due to features like flexibility, ultra-thin profile, very low volume, tilted beam with high gain, and wideband operation, the proposed antenna is highly suitable for beyond fifth-generation (B5G) radio stripe applications.